Repeat mapping of a rural property near Delta, Colorado

Capture

Five visits over 19 months, all flown with the same DJI Phantom 4 Pro (FC6310, 1-inch 20 MP RGB, 8.8 mm lens) on firmware v01.07.1641.

The first mapping flight ran from 15:54 to 19:04 local and produced 1,831 images at 5472 × 3648, at a median 39.5 m above takeoff (30–40 m per the image metadata), 1,277 nadir and 554 oblique, at ISO 100. The second ran 14:18 to 20:11 and produced 1,508 images at a median 39.6 m, 1,150 of them nadir, at ISO 100–160. Image spacing in the processing logs – 7.6 m along track, 5.7 m between lines, over a 57.5 × 38.3 m footprint – works out to roughly 80% forward and 90% side overlap, assuming the standard grid orientation.

The three follow-up visits were lighter: 4K video and 43 oblique stills between 3 and 57 m; then 9 stills and 13 clips; then a 255-image nadir dataset at 22.7 m above takeoff in JPEG and DNG, collected as machine-learning training data.

Georeferencing came from the on-board image geotags alone (WGS 84 / UTM zone 13N). A GNSS base-and-rover session was run – 6 base points, 11 rover points, a 2.065 m pole – but was not applied, for the reasons set out in the accuracy section. Conditions were daylight VFR with low wind, good visibility and high ceilings on every visit, on the operator’s record; the archive holds no weather log.

Deliverables

The first mapped set, a rapid project processed overnight, produced an orthomosaic GeoTIFF (4-band RGBA, 4.19 cm/px, 10,981 × 9,614 px, 280 MB), a float32 DSM at the same resolution (94 MB), both in EPSG:32613 with .tfw/.prj and 5,000-px tiles, an LAS point cloud and an 8-page Pix4D report. The full first project calibrated 1,563 of 1,831 images at 1.00 cm GSD over 29.9 ha / 73.8 acres.

The second mapped set produced an orthomosaic at 4.27 cm/px (12,682 × 20,950 px, 520 MB), a float32 DSM at 168 MB, EPSG:32613 with tiles, an LAS point cloud and a 10-page report: 1,311 of 1,478 images calibrated at 1.07 cm GSD over 31.8 ha / 78.7 acres. Both orthomosaics were exported at four times the native GSD, about 4.2 cm/px from roughly 1.05 cm imagery.

One visit produced video instead: an edited 4K reel of 2 min 26 s and 42 edited stills. The final visit produced a raw image dataset only, with no map products.

Cadence

Recurring. Five visits over 19 months; two of the five produced map products.

Method boundary

These are RGB photogrammetry products georeferenced from the aircraft's own GNSS geotags. Positions are consistent within the model but are not tied to independent ground control, so absolute position can be off by metres, especially in height. The products are suitable for visual record, planning sketches, relative measurement of features, change comparison between visits, and communication with contractors. They are not suitable for boundary or easement determination, engineering design, pay-quantity volumes, or any deliverable that carries professional responsibility. Work of that kind is routed through a licensed Professional Land Surveyor.