So I flew a high school football field to take photos of their new turf field. Airspace only allowed flight altitude of 150 AGL so I could not get the entire field in a true vertical shot due to those low flight restrictions so I decided to create an ortho to generate that vertical image. Everything came out great and I converted the GeoTiff to a JPEG. Then just for the heck of it I decided to bring the GeoTiff into QGIS and look at the relative accuracy of the ortho compared to the football field lines. This project was flown at 125 Ft AGL (0.4 in / px) with no ground control. To my amazement when I measured the 100 yard football field it only measured 93 yards in QGIS! Now I understand that with no ground control the spatial relevance of the project with be based the the autonomous GPS position plus or minus a few meters from the real world spatial coordinated. However, I though that the relative accuracy would be a lot tighter than 7 yards error in a 100 yard measurement. Am I missing something here?
Here is the GEOTiff: