Post

6 followers Follow
0
Avatar

GCPs

You previously mentioned that the usage of trimble geoexplorer 6000 or garmin gpsmap is a good solution for GCPs, here I wana ask you about using trimble device like Geo 7x with a Post-Correction feature ( with a yearly subscription ) Do you think we need that feature (post correction) or the read Real Time value will be more than enough thru 6 or 7x series ?
( I don't have too much idea about trimble instruments 6 nor 7x )
Thanx;

Zahi Khawand

Official comment

Avatar

We are not familiar with that service, but I would caution against expecting too much precision out of any photogrammetric solution at this point. It is likely that the realtime value will be more than enough.

The points defined by the GCPs are simply used as anchor points where we try to minimize their error. Even the GCPs are not guaranteed to be right on the defined coordinates.

The image based reconstruction is the same whether or not GCPs are used. The GCPs are only used to align the rendered solution to real world coordinates. Not stretching or scaling is done based on the GCP definitions.

Tudor
Comment actions Permalink

Please sign in to leave a comment.

5 comments

0
Avatar

Ok, the GCP's we collect on the ground are produced with an RTK network, our surveyed points measured in the millimeters of Decimal Degrees, DMS, WGS 84, NAVD88 are XYZ.

To clarify, these points are not being used to orthorectify the raw UAS, UAV, Drone imagery when uploaded into our Maps Made Easy projects?

Karl Engstrom - CEO
Terra Imaging Inc.

FAA approved for commercial UAV operations - 2015

Karl Engstrom 0 votes
Comment actions Permalink
0
Avatar

The scene reconstruction occurs and then the the GCPs are used to align it to the coordinates. If the real world shape the GCPs create does not match the shape that on the ground stretching will not occur and the error will be minimized between the points.

Tudor 0 votes
Comment actions Permalink
0
Avatar

We're hoping that GCP's would help to rectify elevation errors on our DEM caused by canopy. We're mainly using this data for slope analysis for maximizing usable crop area within certain slope constraints.

My question is will GCPs help to even out elevation discrepancies?

Thank you!

Karl Alexander 0 votes
Comment actions Permalink
0
Avatar

Photogrammetry will not penetrate vegetation since it is based on what is seen in the images. GCPs won't help this. Even if you manually measure GCP locations the uneven terrain due to the presence of vegetation will still be there.

Zane 0 votes
Comment actions Permalink