Photogrammetry and Remote Sensing
Geometry of a vertical photograph
Scale is S = f / (H - h_ground), where f is focal length and H is flying height above datum, so flying height above terrain must be used and the scale therefore varies with relief. Relief displacement is d = r x h / H, measured radially from the principal point, and is zero at the nadir. Parallax p = x_left - x_right, and height differences follow from dp: dh = dp x H / (b + dp). Vertical accuracy is governed by the base-height ratio B/H - the larger the ratio, the stronger the height determination.
Flight planning
Standard vertical photography uses 60% endlap and 25-30% sidelap. Ground coverage per frame = format x scale denominator; air base = ground coverage x (1 - endlap fraction). Many questions hinge on using overlap correctly.
Orientation and products
Workflow: interior orientation (focal length, principal point, lens distortion), relative orientation, absolute orientation using ground control points, then bundle block adjustment for aerotriangulation, DTM/DSM extraction and orthorectification. Traps: confusing a DTM (bare earth) with a DSM (includes vegetation and buildings); forgetting that orthorectification requires a DEM; assuming more GCPs always beats better-distributed GCPs.
Remote sensing
Know the four resolutions - spatial, spectral, radiometric and temporal - and that finer spatial resolution is not automatically better radiometry. Supervised classification needs training samples; unsupervised classification clusters without them. Accuracy is reported through a confusion matrix giving overall accuracy, producer's accuracy (omission, by row in the usual layout), user's accuracy (commission, by column) and the Kappa coefficient.
Worked example
f = 152 mm and flying height above ground 3000 m gives S = 0.152/3000, about 1:19 737. A 23 cm frame then covers roughly 4.5 km x 4.5 km, and at 60% endlap the air base is about 1.8 km.