Mapping and Platting
Scale and map content
Every map question starts with scale. A representative fraction of 1:2,400 means 1 unit on the map equals 2,400 units on the ground; one inch equals 200 ft. Converting between engineer's scale (1 in = 50 ft), graphic scale, and representative fraction is routine. Remember that areas scale as the square of the linear factor: a parcel of 2 in² on a 1:1,200 map covers 2 × (100 ft)², not 2 × 100 ft.
Topographic maps
Contour interval is the vertical distance between adjacent contours; index contours are heavier and labeled. Contours never cross, are perpendicular to the direction of steepest slope, and form closed loops around hills or depressions (hachures mark depressions). A uniform spacing indicates a uniform slope; closely spaced contours indicate steep terrain. Spot elevations supplement contours.
Plats and legal descriptions
A record plat typically shows the boundary with bearings and distances, lot and block layout, dedication of right-of-way, curve data (radius, arc, chord, delta), bearings and distances of all lines, adjoining plats, north arrow, scale, legend, and the owner's certificate, surveyor's certificate and seal, and the approval block. Legal descriptions must close and be self-contained; metes and bounds versus lot-and-block versus aliquot-part descriptions each carry their own conventions. Deliverables must state the datum, units, and whether the file is a recordable plat or a working map.
Worked example
A map at 1:2,400 with 1 in = 200 ft: a measured map distance of 1.75 in corresponds to 350 ft on the ground.