A single AeroPoint can cover up to 100 acres (40 hectares) if the AeroPoint is centrally located and if there is less than 50 ft (15 m) of topographic variation throughout the site. The expected accuracy for one to three AeroPoints on 100 acres is 1/10ft or 3cm.
When on a local grid, we recommend using three AeroPoints to correct for the small amount of error related to the rotation scale and planar shift in locally calibrated sites.
You can add checkpoints (CPs) to help benchmark accuracy between AeroPoints.
Standard Site
Total area: less than 150 acres (60 hectares)
1-3 AeroPoints establish expected accuracy for a site < 100 acres (40 hectares). Larger sites require additional ground control.
** If you are using a local site calibration and processing your data using the Local Site Survey Benchmark (known point) method, using the same location for every flight is best practice.
*** Propeller encourages the collection of multiple checkpoints in between your AeroPoints for more comprehensive insight of accuracy along the site. These can be collected on key surfaces and deltas will display in the GCP and Checkpoints Accuracy section of the Processing Report. AeroPoints can be used as checkpoints!
Large Site
Total area: 100 acres to 300 acres (40 to 120 hectares)
Place one to two AeroPoints every 50 acres (20 hectares) to maintain whole site accuracy.
Distribute the AeroPoints evenly across the site, horizontally and vertically.
Checkpoints (CPs) are your friend! CPs help our teams conduct quality control on the data and note any shifts between surveys.
** If you are using a local site calibration and processing your data using the Local Site Survey Benchmark (known point) method, using the same location for every flight is best practice.
*** Propeller encourages the collection of multiple checkpoints in between your AeroPoints for more comprehensive insight of accuracy along the site. These can be collected on key surfaces and deltas will display in the GCP and Checkpoints Accuracy section of the Processing Report. AeroPoints can be used as checkpoints!
Massive Site
Total area: over 300 acres (120 hectares)
For sites larger than 300 acres, you must leapfrog your AeroPoints to cover the whole site.
If you do this, you must first place a known point (benchmark) down. Pick up this AeroPoint last. It has to be on and undisturbed for the whole survey, which has a five hour time limit (eight hour limit for AeroPoint 2s).
The others can be turned off, moved, and turned back on to continue the survey. Your AeroPoints should be placed every 50 acres (20 hectares).
AeroPoints can "leapfrog" as you advance along a corridor. Propeller recommends the benchmark AeroPoint be located in a more central location when flying these larger sites and leapfrogging.
Please contact your customer success representative for assistance with leapfrogging on a very large site.
I still can't do it!
We wrote these articles to equip you with everything you need to get the job done on your own, but we understand that sometimes this isn't sufficient.
If you're stuck, the Propeller hardware support team may be able to help. You can contact them by emailing hardwaresupport@propelleraero.com.au.