Orthorectifying Aerial Photographs

Question

HI,

I use a UAV to take some aerial images, but I want to use this images to be able to measure true distances and for that purpose I have to orthorectify them. I looked in the the help menu in ArcGIS and it says that what I need are the RPC's (rational polynomial coefficients) and a DEM, also some control points would help make an accurate orthophoto.

What I need help with is creating this RPC's, because I have no idea what they are and they seem to be the key to all of this. Can anyone out there help me by telling me what RPC's are, and how to create them in a proper way that ArcGIS identifies it as part of the raster image I upload.

Thanks,

SantiagoTrujillo · Answer

Generally speaking, the RPC or rational polynomial coefficients are created by the sensor, usually a satellite.  In most cases, the RPCs are included with satellite imagery, as mentioned here.  In terms of ortho rectifying your UAV data, then if the RPCs were not generated in the process then you must find a way to create check points based on surveyed ground control points that should have ideally been collected prior to flying the project.  There are other software packages that can help you orthorectify with manually added checkpoints, like ENVI.

Yeah I was beginning to think I would have to use another software to orthorectify my images. I saw some ENVI tutorial and they did show how to do it manually, but still there must be some way to create this RPC's from the information the UAV gives me (altitude, lat and long) and the information of the camera. If someone has information on how to create RPC's  from your own aerial photographs it would be really helpful.

Anyway thanks for your help I'll give it a try using ENVI and if it works then maybe there'll be no need to create RPC's to be read on ArcGIS.

JeffreySwain · Answer

Generally speaking, the RPC or rational polynomial coefficients are created by the sensor, usually a satellite.  In most cases, the RPCs are included with satellite imagery, as mentioned here.  In terms of ortho rectifying your UAV data, then if the RPCs were not generated in the process then you must find a way to create check points based on surveyed ground control points that should have ideally been collected prior to flying the project.  There are other software packages that can help you orthorectify with manually added checkpoints, like ENVI.