GCP Points - Something stupid?

[MrFilson]

Might sound stupid but its worth asking.

Anyone tried shooting aerial images with their GPS enabled camera then using the same camera on the ground, shooting straight down at visible objects that can be seen in the aerial imagery (center of a manhole for instance or any other identifiable object) say from the exact same height, 1 or 2 meters off the ground, consistently all over the project area? You could collect as many points as you wanted in a very short amount of time with no expensive survey gear.

Then using those pics gps data, identify the objects / locations in the aerial images, and then enter the gps data from that corrisponding pic into the project.

If you went all over the project area and shot all these pics and then used their gps data Im wondering about what kind of accuracy you would get. Same receiver, same camera, same everything. Ive test shot this and the gps data (elevation too) is pretty consistent and seems to match the terrain fairly accurately.

Im curious if this would work for creating "rough" (not super accurate) but better quality DEM's and other output data?

Sounds to good to be true but Im not looking for dead nuts accuracy, not yet anyway.  Just getting started with PS.

Its obviously a very cheap, quick, and inaccurate way to get some Ground Control but I'm wondering if its better than having nothing at all.






Just curious.

[frank.stremke]

hello
if you are fine with general GPS accuracy then why bother with this procedure. for some projects where the +- of a few meters do not matter then you can just use the cammera GPS coordinates of the pictures by using the import exif data. then you can work without any Ground control points i do thet in order to have my model coursly alligned to my markers so i can find them quick but it also gives good results without ground control points
so at least you can save the walking around :-) also since the time between the gps mesurements is just very short (seconds) at least the acuuracy whithin the model should be ok at least as far as exif alows you since the coordinate precission is limited.
best regards
frank

[MrFilson]

I pretty much new that the on ground GCP would be just as off as the aerial gps data. Two wrongs couldn't make a right but I thought that I would ask.

Im looking for the ideal inexpensive way of doing some of the walking around and getting solid GCP. Ive got access to a sub-meter Trimble unit and Bluemarble is telling me that there Global Mapper will correct that units output if I use my laptop hooked up to it to record my GCP's.

Too what level of accuracy it will do it I'm not for sure of yet. I may be complexity off track here on getting solid GCP, I don't know. Any help at all will be of great help.