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GISI Foundation practice questions

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Question 1Geographic Information Systems and Spatial Data Fundamentals

A raster dataset stores elevation values on a 30 m grid. What does a single cell value represent?

  1. The elevation of only the cell's north-west corner point
  2. The distance from the cell to the nearest contour line
  3. The elevation for the whole area covered by that cell Correct answer.
  4. The average elevation across the entire dataset extent

Explanation

In a raster, each cell holds one attribute value that is treated as applying uniformly across the whole cell footprint. For elevation, that value is normally a summary (often the mean) of the ground surface within the cell, not a single point reading or a dataset-wide statistic.

Question 2Geographic Information Systems and Spatial Data Fundamentals

Which coordinate pair uses a geographic coordinate system rather than a projected one?

  1. Row 214, column 388 in a raster grid
  2. Latitude 51.5074 degrees north, longitude 0.1278 degrees west Correct answer.
  3. X = 699000, Y = 571000 in feet
  4. Easting 512340, northing 4310220 in metres

Explanation

Geographic coordinate systems locate positions as angular measures of latitude and longitude on a reference ellipsoid. Projected systems express positions as linear easting/northing distances from an origin, and raster row/column indices are storage coordinates rather than either.

Question 3Geographic Information Systems and Spatial Data Fundamentals

In a vector data model, which geometry type is appropriate for representing a river network where flow direction and connectivity matter?

  1. Polygon
  2. Raster cell
  3. Point
  4. Line (arc) Correct answer.

Explanation

Lines are one-dimensional features with two endpoints and a defined order of vertices, so they can carry direction and connect at shared nodes. That topology makes them the standard choice for networks such as rivers, roads, and utility mains.

Question 4Geographic Information Systems and Spatial Data Fundamentals

A dataset is described as having a positional accuracy of plus or minus 5 metres at 95% confidence. What does this statement mean?

  1. About 95% of tested positions fall within 5 metres of their true location Correct answer.
  2. Every coordinate in the dataset is wrong by exactly 5 metres
  3. The dataset resolution is 5 metres per cell
  4. The dataset may only be used for scales finer than 1:5000

Explanation

Positional accuracy is a statistical statement about the distribution of error, not a fixed offset. A 95% confidence figure means roughly 19 in 20 checked positions lie within the stated distance of truth, while about 5% may fall outside it.

Question 5Geographic Information Systems and Spatial Data Fundamentals

Which file format stores both geometry and attribute data in a single self-describing file and is widely used for GIS data exchange?

  1. Comma-separated values (.csv)
  2. Tagged image file format (.tif)
  3. GeoJSON (.geojson) Correct answer.
  4. Plain text (.txt)

Explanation

GeoJSON is a structured text format that encodes geometry together with a properties object holding attributes, so a single file is self-describing. It is designed for interoperability and is broadly supported by GIS software and web mapping tools.

Question 6Geographic Information Systems and Spatial Data Fundamentals

Which map element explains the meaning of the symbols used on a thematic map?

  1. The graticule
  2. The legend Correct answer.
  3. The scale bar
  4. The north arrow

Explanation

The legend, sometimes called the key, pairs each symbol, colour, or pattern with the class or category it represents. Without it a reader cannot reliably decode a thematic map's symbology.

Question 7Geographic Information Systems and Spatial Data Fundamentals

What is the primary purpose of a spatial index such as an R-tree in a GIS database?

  1. To reproject coordinates between reference systems
  2. To enforce attribute domain rules on a table
  3. To speed up spatial queries by reducing the features that must be tested Correct answer.
  4. To compress raster imagery without losing detail

Explanation

A spatial index stores bounding-box summaries of features in a hierarchical structure so a query can discard most candidates without examining their full geometry. This turns a full scan into a much smaller set of exact geometry tests, which is the main performance gain.

Question 8Geographic Information Systems and Spatial Data Fundamentals

Which vector overlay operation returns only the areas that fall inside both input polygons?

  1. Intersect Correct answer.
  2. Symmetrical difference
  3. Erase
  4. Union

Explanation

Intersect keeps the portions of features that overlap in both inputs and discards the remainder, along with attributes from both layers. It is the standard overlay for finding shared area between two polygon datasets.

Question 9Geographic Information Systems and Spatial Data Fundamentals

A vector parcel layer and a raster land-cover layer are combined so each parcel reports the majority land-cover class within it. Which approach is appropriate?

  1. Rasterize the parcel layer at a coarse cell size and compare class counts
  2. Convert the land cover to polygons and clip it to the parcel bounding box
  3. Buffer the parcels by the raster cell size and dissolve the result
  4. Zonal statistics using the parcels as zones and the land cover as the value raster Correct answer.

Explanation

Zonal statistics summarises raster cell values within each zone polygon, and a majority statistic returns the most frequent class per zone. That directly produces one land-cover class per parcel without altering either input's geometry.

Question 10Geographic Information Systems and Spatial Data Fundamentals

A raster is in a projected CRS with 10 m cells. A slope tool reports a value of 0.15 for a cell. How should this be interpreted if the tool outputs rise over run in the raster's linear units?

  1. A 15 degree slope
  2. A 15 percent slope
  3. A 0.15 metre rise per 10 metre cell, i.e. a ratio of 0.15 Correct answer.
  4. A slope that cannot be interpreted without the cell area

Explanation

Rise-over-run output is a dimensionless ratio, so 0.15 means the surface rises 0.15 linear units for every one unit travelled horizontally. Over a 10 m cell that is a 1.5 m rise, and the ratio is independent of cell area.

Question 11Geographic Information Systems and Spatial Data Fundamentals

Two adjacent polygons in the same layer share a boundary, but after an edit a narrow sliver gap appears along that boundary. What is the most appropriate description of this problem?

  1. A raster resolution mismatch between the two polygons
  2. An attribute domain violation on the polygon identifier
  3. A topology error in the form of a gap between polygons that should be contiguous Correct answer.
  4. A projection error caused by using the wrong datum

Explanation

Topology rules define expected spatial relationships such as adjacency without gaps or overlaps. A sliver between polygons that should share an edge violates that adjacency rule and is a classic topology error to be validated and corrected.

Question 12Geographic Information Systems and Spatial Data Fundamentals

A coordinate transformation is applied to a dataset using a datum transformation with no parameters supplied. What is the most likely consequence?

  1. The geometry is reprojected but positions may be offset by the datum shift Correct answer.
  2. The coordinate values are rounded to whole metres
  3. The dataset is automatically densified along every vertex
  4. The attribute table is reordered to match the new projection

Explanation

Changing projection without an appropriate datum transformation leaves the datum shift unaccounted for, producing a systematic positional offset that can reach tens or hundreds of metres. The geometry is still transformed mathematically, so the error is silent unless checked against control points.

Question 13Geographic Information Systems and Spatial Data Fundamentals

Which spatial analysis operation would you use to determine which customers fall inside a newly drawn sales territory polygon?

  1. Select by location with the customers as the target and the territory as the source Correct answer.
  2. Dissolve the customers by their postcode
  3. Spatial join of the territory onto itself
  4. Buffer the customers by the territory's area

Explanation

Select by location tests a spatial relationship such as within or intersect between a target layer and a source layer, returning the customers inside the polygon. It answers the containment question directly without modifying geometry.

Question 14Geographic Information Systems and Spatial Data Fundamentals

A dataset of points is stored in a geographic CRS in decimal degrees. A buffer of 500 metres is required. Why is buffering directly in degrees problematic?

  1. Decimal degrees have insufficient precision for any distance work
  2. Degrees cannot store negative values
  3. Buffers in geographic coordinates always fail to close
  4. One degree of longitude covers a distance that varies with latitude, so a degree buffer is not a constant ground distance Correct answer.

Explanation

Angular units do not map to a constant linear distance: a degree of longitude shrinks toward the poles while a degree of latitude stays roughly constant. Buffering in degrees therefore yields a ground distance that changes with location, so the data should be projected to a suitable linear CRS first.

Question 15Geographic Information Systems and Spatial Data Fundamentals

A DEM contains sinks, and a flow-accumulation tool produces disconnected drainage lines. Which preprocessing step is normally required first?

  1. Fill or breach the sinks to create a hydrologically correct surface Correct answer.
  2. Apply a low-pass filter to smooth the elevation values
  3. Convert the DEM to a vector contour layer
  4. Resample the DEM to a coarser cell size

Explanation

Flow-routing algorithms require a surface where every cell drains to an outlet, so depressions must be removed by filling or breaching. Leaving sinks in place traps flow and breaks the accumulation network into disconnected pieces.

Question 16Geographic Information Systems and Spatial Data Fundamentals

Which statement best distinguishes the vector and raster models for representing a continuous field such as temperature?

  1. Vector cannot represent continuous fields under any circumstances
  2. Raster stores a value for every cell in a regular grid, while vector typically stores sampled points or polygons with values Correct answer.
  3. Vector stores a value at every location via cells, while raster stores only sampled points
  4. Both models store continuous fields only as polygons

Explanation

A raster represents a continuous field by assigning a value to every cell in a regular grid, giving complete coverage. Vector representations sample the field at points or delineate areas as polygons, which is efficient but does not by itself provide a value everywhere.

Question 17Geographic Information Systems and Spatial Data Fundamentals

A layer of 1000 points is thinned so that no two retained points lie within 200 metres of each other. Which operation performs this?

  1. Densifying the points along a 200 metre interval
  2. Spatial clustering into 200 metre groups
  3. Aggregating the points to a 200 metre grid without a rule
  4. Point thinning with a minimum spacing of 200 metres Correct answer.

Explanation

A minimum-spacing thinning rule removes points that fall within the specified distance of an already retained point, enforcing the separation. The result is a subset of the original points rather than new or merged features.

Question 18Geographic Information Systems and Spatial Data Fundamentals

A polygon layer and a line layer are intersected to find road segments crossing protected areas. Which output geometry type is produced by a standard intersect operation?

  1. Polygons representing the protected areas
  2. Line segments clipped to the portions inside the polygons Correct answer.
  3. The original lines unchanged with no clipping
  4. Points at the crossing locations only

Explanation

Intersect returns the coincident portion of the inputs, so lines are split and clipped to the parts that lie within the polygons while retaining attributes from both layers. The output geometry is therefore line, not point or polygon.

Question 19Geographic Information Systems and Spatial Data Fundamentals

Which statement correctly describes the difference between spatial resolution and spatial extent in a raster?

  1. Resolution is the total area covered; extent is the ground size of one cell
  2. Resolution is the number of bands; extent is the number of rows
  3. Resolution and extent are synonyms for raster dimensions in rows and columns
  4. Resolution is the ground size of one cell; extent is the total area covered by all cells Correct answer.

Explanation

Spatial resolution describes the ground footprint of a single cell, while spatial extent is the overall area spanned by the full grid. A raster can have a small cell size (fine resolution) over a small extent, or a large cell size over a large extent.

Question 20Geographic Information Systems and Spatial Data Fundamentals

A map is to be published at 1:25 000 and the source data has a positional accuracy of about 12 metres. What is the most appropriate assessment?

  1. The data accuracy is broadly adequate, since 12 metres is about 0.5 mm on the printed map Correct answer.
  2. The data is far too accurate for this scale and should be generalised
  3. The data must be reprojected to a geographic CRS before use
  4. The data cannot be used because accuracy must always be finer than 1 metre

Explanation

At 1:25 000, one millimetre on the map represents 25 metres on the ground, so 12 metres is roughly 0.5 mm, below the usual threshold of visual discrimination. The data accuracy is therefore appropriate for publication at that scale.

Question 21Geographic Information Systems and Spatial Data Fundamentals

Which operation creates a new polygon layer containing all areas from two input layers, with attributes from both retained wherever they overlap?

  1. Intersect
  2. Clip
  3. Union Correct answer.
  4. Dissolve

Explanation

Union combines the full extent of both polygon layers and keeps attributes from each input in the overlapping portions. The output includes areas unique to either input as well as shared areas.

Question 22Geographic Information Systems and Spatial Data Fundamentals

A spatial join transfers an attribute from a polygon layer to a point layer. What determines which polygon's attribute each point receives?

  1. The alphabetical sorting of the polygon identifiers
  2. The order of records in the attribute table
  3. The spatial relationship between each point and the polygons, such as containment Correct answer.
  4. The number of vertices in each polygon

Explanation

A spatial join matches records by a spatial predicate, typically whether a point falls within a polygon, and copies attributes from the matching feature. Record order, identifier sorting, and vertex counts play no role in the match.

Question 23Geographic Information Systems and Spatial Data Fundamentals

A raster cost surface is used for least-cost path analysis. Which interpretation of cell values is required for the algorithm to work correctly?

  1. Values represent the cost per unit distance of moving through each cell Correct answer.
  2. Values represent the number of features in each cell
  3. Values must be integers between 0 and 255
  4. Values must be elevations in metres

Explanation

Least-cost path analysis accumulates cost as a function of the friction value in each cell multiplied by the distance travelled through it. The surface therefore encodes relative impedance to movement, not elevation or feature counts.

Question 24Geographic Information Systems and Spatial Data Fundamentals

Two polygon layers are expected to share a boundary exactly, but one has vertices at 10 m intervals while the other has vertices at 3 m intervals along the same line. Which issue is most likely to arise?

  1. A datum mismatch between the two layers
  2. Sliver polygons or false gaps caused by non-coincident vertex densification Correct answer.
  3. An incorrect raster cell size assignment
  4. A failure of the attribute table to store text fields

Explanation

When shared boundaries have different vertex spacing, the two lines may not coincide exactly between vertices, so overlay operations produce thin slivers or false gaps. Snapping or topology-based integration is normally used to align the boundaries before analysis.

Question 25Geographic Information Systems and Spatial Data Fundamentals

A viewshed is computed from a single observer point on a DEM. Which factor most directly limits the reliability of the result in steep terrain?

  1. The vertical accuracy and resolution of the DEM relative to terrain roughness Correct answer.
  2. The colour ramp chosen for the output
  3. The projection of the observer's attribute table
  4. The number of attribute fields in the observer point layer

Explanation

Viewshed analysis tests line of sight against the terrain surface, so errors in elevation and coarse cell size can block or open sight lines incorrectly, especially where relief is steep. Symbology and attribute structure do not affect the geometric computation.

Question 26Geographic Information Systems and Spatial Data Fundamentals

Which property of the GeoJSON format makes it well suited to exchanging vector features between web mapping libraries?

  1. It embeds a fixed raster grid beneath each vector feature
  2. It compresses every coordinate pair to a single floating-point value
  3. It requires a proprietary binary header before any coordinates are read
  4. It stores geometry and attributes together as structured text that browsers can parse directly Correct answer.

Explanation

GeoJSON is a text-based encoding built on JSON, so geometry coordinates and feature attributes travel together in one document that web clients can parse without a dedicated binary reader. This portability, rather than compression or embedded imagery, is why it is widely used for lightweight vector interchange.

Question 27Geographic Information Systems and Spatial Data Fundamentals

A dataset must be stored so that each pixel holds exactly one land-cover class code and the boundaries between classes stay crisp. Which data model fits this requirement?

  1. A triangulated irregular network of class centroids
  2. A floating-point raster holding interpolated class values
  3. An integer raster with class codes stored per cell Correct answer.
  4. A point layer with one point per class boundary vertex

Explanation

Categorical fields are best held in an integer raster where each cell stores a discrete class code, preserving sharp boundaries between classes. Interpolated floating-point surfaces or vertex-based structures blur or misrepresent categorical distinctions.

Question 28Geographic Information Systems and Spatial Data Fundamentals

Which coordinate pair is expressed in a geographic coordinate reference system rather than a projected one?

  1. Easting 4 312 500, northing 2 245 800
  2. X 512 340, Y 4 678 210 in metres
  3. Zone 33U, easting 291 000, northing 4 640 000
  4. Longitude 12.4964, latitude 41.9028 Correct answer.

Explanation

Geographic coordinate systems record position as angular longitude and latitude values in degrees. The other entries use linear easting and northing values, which are characteristic of projected systems such as UTM.

Question 29Geographic Information Systems and Spatial Data Fundamentals

A GIS technician needs to record that a road centreline dataset was digitised from a 1:50 000 topographic map. Which metadata element captures this information?

  1. Lineage describing the source materials and derivation process Correct answer.
  2. The default label font used on the map
  3. The number of vertices in each feature
  4. The layer's display symbology settings

Explanation

Lineage is the metadata element that documents where data came from and how it was produced, including source map scale and derivation steps. Symbology, vertex counts, and fonts describe presentation or geometry, not provenance.

Question 30Geographic Information Systems and Spatial Data Fundamentals

A polygon layer of census tracts is joined to a table of population totals using a shared tract identifier field. Which join type is being performed?

  1. A spatial join based on containment
  2. A raster-to-vector conversion
  3. A relational attribute join on a key field Correct answer.
  4. A nearest-neighbour spatial join

Explanation

When records are matched through a shared attribute such as a tract identifier, the operation is an attribute (relational) join and no geometry is involved. Spatial joins instead use geometric relationships such as containment or proximity to decide matches.

Question 31Geographic Information Systems and Spatial Data Fundamentals

A vector layer of rivers is converted to a raster with 30 m cells using a line rasterisation algorithm. What is the most likely consequence for narrow rivers?

  1. Each river is represented by a chain of cells whose width no longer reflects the true channel width Correct answer.
  2. Each river becomes a polygon with vertices at every cell corner
  3. Each river retains sub-cell width accuracy through fractional cell values
  4. Each river disappears entirely because lines cannot be rasterised

Explanation

Rasterising a line assigns whole cells to the feature, so the resulting representation is at least one cell wide regardless of the true channel width. Detail finer than the cell size is therefore lost and widths are exaggerated or generalised.

Question 32Geographic Information Systems and Spatial Data Fundamentals

A point layer of wells and a polygon layer of aquifers are compared, and a well lying exactly on a shared aquifer boundary must be assigned to only one aquifer. Which approach resolves this cleanly?

  1. Buffer the well by one cell width before testing containment
  2. Assign the well to both aquifers so no information is lost
  3. Assign the well to neither aquifer and flag it as unclassified
  4. Apply a defined rule such as assigning boundary cases to the polygon with the lower identifier Correct answer.

Explanation

Boundary cases produce ambiguous containment tests, so a deterministic tie-breaking rule ensures each point receives exactly one polygon and results are reproducible. Assigning duplicates or dropping the record breaks the one-to-one requirement.

Question 33Geographic Information Systems and Spatial Data Fundamentals

Which statement correctly describes how a topology rule benefits a geodatabase of land parcels?

  1. It reprojects parcels automatically whenever the map is zoomed
  2. It detects and reports violations such as gaps or overlaps between parcels that should share clean boundaries Correct answer.
  3. It stores the parcel attributes in a separate non-spatial table
  4. It converts parcel polygons into raster cells for display

Explanation

Topology rules encode spatial relationships that must hold, such as polygons not overlapping, and validation reports features that violate them. This supports data quality control rather than display, reprojection, or attribute storage.

Question 34Geographic Information Systems and Spatial Data Fundamentals

A raster of elevation is resampled from 5 m to 20 m cells for a regional model. Which resampling method is most appropriate for preserving the continuous surface?

  1. Bilinear interpolation of the four contributing cells Correct answer.
  2. Assignment of the minimum value among the contributing cells
  3. Majority vote among the contributing cells
  4. Nearest-neighbour assignment of the closest cell value

Explanation

Continuous surfaces such as elevation are best resampled with interpolation, which produces a smooth surface from the contributing cells. Nearest-neighbour, majority, and minimum rules are suited to categorical data and would introduce artefacts in a continuous field.

Question 35Geographic Information Systems and Spatial Data Fundamentals

A GIS analyst needs to identify all parcels within 250 metres of a proposed pipeline route, measured as straight-line distance from the route. Which operation produces this result?

  1. Generate a Thiessen polygon layer from parcel centroids
  2. Clip the parcels to the pipeline route
  3. Dissolve the parcels by land-use code
  4. Buffer the pipeline route at 250 metres and select parcels that intersect the buffer Correct answer.

Explanation

A buffer creates a zone at a specified distance from a feature, and selecting parcels that intersect that zone answers the proximity question. Clipping, dissolving, and Thiessen polygons address different analytical goals.

Question 36Geographic Information Systems and Spatial Data Fundamentals

A raster stores values in a projected CRS with 25 m cells. A distance-allocation tool is run without specifying cell size. What distance does one cell of cost represent?

  1. 25 metres, because the cell size defines the ground distance per cell Correct answer.
  2. The value stored in the cell, because cost replaces distance
  3. 1 metre, because raster distance is always unitless
  4. 625 square metres, because area rather than length is used

Explanation

For a projected raster, the cell size gives the ground length represented by one cell, so with 25 m cells each step corresponds to 25 metres on the ground. Area and stored cost values do not define the geometric step length.

Question 37Geographic Information Systems and Spatial Data Fundamentals

A hillshade is generated from a DEM to support visual interpretation of terrain. Which input controls the direction from which the simulated illumination appears to come?

  1. The cell size of the output raster
  2. The z-factor, which scales vertical exaggeration
  3. The azimuth parameter, expressed in degrees clockwise from north Correct answer.
  4. The resampling method used on the DEM

Explanation

Hillshade azimuth sets the compass direction of the simulated light source, measured clockwise from north, and therefore controls which slopes appear lit or shadowed. Z-factor, cell size, and resampling affect intensity or geometry but not illumination direction.

Question 38Geographic Information Systems and Spatial Data Fundamentals

Two vector layers use different datums, and a transformation is applied that shifts features by several tens of metres. Which statement best explains the resulting positional change?

  1. The same physical location has different coordinate values under each datum, so converting between them moves the coordinates Correct answer.
  2. The datum transformation changes the map scale but not the coordinates
  3. The transformation rotates the map display without changing stored coordinates
  4. The features have been edited and their geometry altered by the analyst

Explanation

A datum defines the reference surface and origin used to assign coordinates, so a physical point has different coordinate values under different datums. Transforming between datums therefore changes stored coordinate values by an amount that depends on the datum pair.

Question 39Geographic Information Systems and Spatial Data Fundamentals

A suitability model combines a slope raster and a distance-to-road raster after each is rescaled to a common 0-100 range. Why is this rescaling step necessary before weighted summation?

  1. Rescaling removes the need to choose criterion weights
  2. Rescaling converts both rasters from vector to raster format
  3. Rescaling guarantees that the output raster has no NoData cells
  4. The input layers use different units and scales, so raw values would let one criterion dominate the weighted sum Correct answer.

Explanation

Weighted summation assumes comparable value ranges, and slope in degrees is not comparable with distance in metres. Rescaling to a common range lets the chosen weights, rather than the original units, determine each criterion's influence.

Question 40Geographic Information Systems and Spatial Data Fundamentals

A polygon coverage is checked against a boundary line coverage, and the analyst finds that some polygon edges deviate from the line coverage by up to 3 metres. Which explanation is most consistent with this finding?

  1. The line coverage uses a geographic CRS and therefore cannot represent boundaries
  2. The polygon layer has been reprojected while the line layer has not, which always produces exactly 3 metres of offset
  3. The two datasets were captured independently with different vertex densities and positional accuracy, so shared boundaries do not coincide exactly Correct answer.
  4. The polygon layer stores attributes that override its geometry during display

Explanation

Independent capture of the same real-world boundary produces different vertex spacing and small positional errors, so edges that should coincide do not match exactly. This is a data integration problem addressed by snapping or topology building, not a fixed effect of projection or attributes.

Question 41Spatial Reference Systems, Projections, and Coordinate Geometry

In a geographic coordinate system, what does the datum primarily define?

  1. The vertical distance above mean sea level at any point
  2. The map scale factor applied at the central meridian
  3. The relationship between the ellipsoid and the Earth's surface, including its position and orientation Correct answer.
  4. The number of decimal places used to store coordinate values

Explanation

A geodetic datum fixes an ellipsoid of specified size and shape and anchors it to the Earth through an origin, orientation, and (for modern datums) a defined relationship to a terrestrial reference frame. Without the datum, latitude and longitude are ambiguous, since the same numeric coordinates on different datums refer to different physical points.

Question 42Spatial Reference Systems, Projections, and Coordinate Geometry

A dataset of well locations is stored with latitude/longitude values in the WGS 1984 datum, but the field survey was actually referenced to NAD 1927. What is the most significant consequence?

  1. Positions will be systematically offset by up to a few hundred metres in North America Correct answer.
  2. Positions will remain correct but the attribute table will lose its field names
  3. Positions will be rotated by exactly 90 degrees around the prime meridian
  4. Positions will be unaffected because both datums use the same ellipsoid

Explanation

NAD 1927 and WGS 1984 are anchored differently, and the shift between them across North America reaches roughly 10 to 100-plus metres, with larger discrepancies in some regions. Treating NAD 1927 values as WGS 1984 therefore introduces a systematic horizontal error rather than random noise.

Question 43Spatial Reference Systems, Projections, and Coordinate Geometry

Which statement correctly describes the difference between a geographic and a projected coordinate system?

  1. Geographic systems require a projection method; projected systems do not
  2. Geographic systems locate positions on an ellipsoid using angular units; projected systems locate positions on a plane using linear units Correct answer.
  3. Geographic systems use linear units on a plane; projected systems use angular units on an ellipsoid
  4. Geographic systems always preserve area; projected systems always preserve distance

Explanation

A geographic coordinate system expresses position as longitude and latitude (angular measure) relative to a datum. A projected coordinate system applies a map projection to convert those angles into planar coordinates measured in metres or feet.

Question 44Spatial Reference Systems, Projections, and Coordinate Geometry

A Web Mercator (EPSG:3857) tile service is used to display data. Which property does this projection NOT preserve?

  1. Straight-line meridians
  2. True area Correct answer.
  3. Shape of small features near the equator
  4. Right angles between meridians and parallels

Explanation

Web Mercator is conformal, so it preserves local angles and small-scale shape, and meridians appear as straight vertical lines. Scale, and therefore area, increases strongly with latitude, so areas at high latitudes are grossly exaggerated.

Question 45Spatial Reference Systems, Projections, and Coordinate Geometry

Which map projection property is most important when producing a small-scale map intended for measuring areas of land cover classes?

  1. Equal-area (equivalent) Correct answer.
  2. Equidistant along all lines
  3. Conformal
  4. Azimuthal from every point

Explanation

Equal-area projections preserve the ratio of mapped area to true area, so polygon areas computed on the map are proportional to real-world areas. Conformal projections preserve angles but distort area increasingly away from the standard line.

Question 46Spatial Reference Systems, Projections, and Coordinate Geometry

A UTM zone number is known for a location at 45 degrees north latitude. Which parameter set best describes the transverse Mercator projection used for that zone?

  1. Central meridian at the zone's central longitude, scale factor 0.9996, false northing 10000000 m
  2. Central meridian at the zone boundary, scale factor 1.0, false easting 0 m
  3. Central meridian at the equator, scale factor 0.9996, false northing 500000 m
  4. Central meridian at the zone's central longitude, scale factor 0.9996, false easting 500000 m Correct answer.

Explanation

Each UTM zone is a transverse Mercator projection centred on its central meridian with a central scale factor of 0.9996 and a false easting of 500000 m to avoid negative coordinates. The false northing of 10000000 m applies only in the southern hemisphere.

Question 47Spatial Reference Systems, Projections, and Coordinate Geometry

In the UTM system, what is the approximate width in degrees of a single zone?

  1. 3 degrees of longitude
  2. 1 degree of longitude
  3. 6 degrees of longitude Correct answer.
  4. 10 degrees of longitude

Explanation

UTM divides the globe into 60 zones, each spanning 6 degrees of longitude, beginning at 180 degrees west. Each zone is projected separately to keep distortion within acceptable limits.

Question 48Spatial Reference Systems, Projections, and Coordinate Geometry

A point has a UTM northing of 0 m in a southern-hemisphere zone. What does this indicate?

  1. The point lies at the zone's central meridian intersection with the equator only if easting is also 0
  2. The point is invalid, because southern UTM northings are always positive
  3. The point lies on the equator, because 10000000 m is subtracted from the southern false northing Correct answer.
  4. The point is at the south pole, since northing increases northward from zero there

Explanation

Southern-hemisphere UTM applies a false northing of 10000000 m, so a northing of 0 m corresponds to the equator rather than the pole. Northings decrease southward from that value.

Question 49Spatial Reference Systems, Projections, and Coordinate Geometry

Which statement about the State Plane Coordinate System is accurate?

  1. It is defined only for the conterminous United States and excludes Alaska and Hawaii
  2. It uses a single nationwide transverse Mercator projection for all states
  3. It uses different projection parameters for different zones, often transverse Mercator, Lambert conformal conic, or oblique Mercator Correct answer.
  4. It is a geographic coordinate system expressed in degrees

Explanation

SPCS is organised into zones, each with parameters chosen to control distortion for its area, and the projection family varies by zone shape and orientation. Zones may use transverse Mercator, Lambert conformal conic, or oblique Mercator.

Question 50Spatial Reference Systems, Projections, and Coordinate Geometry

What is the geoid?

  1. A perfect mathematical ellipsoid of revolution used for all projections
  2. An equipotential surface of the Earth's gravity field that approximates mean sea level Correct answer.
  3. A plane tangent to the ellipsoid at the projection's origin
  4. The surface of the terrain derived from a digital elevation model

Explanation

The geoid is the equipotential surface of the gravity field that best fits global mean sea level and extends through the continents. Orthometric heights are measured relative to it, while ellipsoidal heights are measured relative to the ellipsoid.