Surveyed GCP data

[Laggard]

Anyone know where I can download csv files with surveyed GCP data?

Thanks

 

[Meta4]

Anyone know where I can download csv files with surveyed GCP data?

Usually you or a surveyor working with you would generate those.
You need the GC points to be in/around the site you are mapping.

 

[BigAl07]

Anyone know where I can download csv files with surveyed GCP data?

Thanks

I'm not following your thought process. Those are created by you (if you're capable) or a survey team for the job/site in question.

If I'm totally missing the boat I apologize as it is late here lol

 

[Laggard]

I'm not following your thought process. Those are created by you (if you're capable) or a survey team for the job/site in question.

If I'm totally missing the boat I apologize as it is late here lol

Maps made easy has what they call “a new way to get highly accurate aerial maps without the cost”. By importing gcp points over an existing image and then adjusting it to match the gcps.

They make it sound like csv files with gcps are just available for anyone to download.

I mean I know where a couple surveyed gcp points are nearby. But that’s about it.

 

[Meta4]

Maps made easy has what they call “a new way to get highly accurate aerial maps without the cost”. By importing gcp points over an existing image and then adjusting it to match the gcps.

They make it sound like csv files with gcps are just available for anyone to download.

Or do they mean for you to generate some GPSs to use together with readily available aerial imagery?
You need the GPSs to be close in/around the imagery.
I don't think you are going to find a handy file of GCPs that just happen to be exactly where you need them.

 

[Laggard]

Or do they mean for you to generate some GPSs to use together with readily available aerial imagery?
You need the GPSs to be close in/around the imagery.
I don't think you are going to find a handy file of GCPs that just happen to be exactly where you need them.

I think you are absolutely right.

Does georeferencing serve the same function?

 

[BigAl07]

Maps made easy has what they call “a new way to get highly accurate aerial maps without the cost”. By importing gcp points over an existing image and then adjusting it to match the gcps.

They make it sound like csv files with gcps are just available for anyone to download.

I mean I know where a couple surveyed gcp points are nearby. But that’s about it.

I'm familiar with MME (and use MME as well as DD) but I couldn't wrap my mind around a publicly available CSV with GCPs.

 

[Debaser_AZ]

The way I understand it, MME touts this feature as a way to use GCPs after a map has been processed, almost like rubber sheeting the ortho. GCPs would still need to be surveyed to be an improvement. The 'GCP' would need to be some immovable target also found on the initial map ('tree stump').

 

[Laggard]

The way I understand it, MME touts this feature as a way to use GCPs after a map has been processed, almost like rubber sheeting the ortho. GCPs would still need to be surveyed to be an improvement. The 'GCP' would need to be some immovable target also found on the initial map ('tree stump').

Agreed

 

[Adam West Aus]

Anyone know where I can download csv files with surveyed GCP data?

Thanks

I'd imagine you could only get that from the Survey company which mapped out the GCPs. Usually you just export the CSV from the GNSS receiver after job completed. With the prices that are charged for surveying I'm not sure this would be a free commodity.

 

[OdysseyShane]

Unfortunately, this is not something you will be able to find, and even if you could, as a surveyor, I would be very careful trusting someone else's data. Fortunately, GCP's aren't necessary for everything, and you can make perfectly adequate, somewhat accurate geographically maps and models. If your requirements actually call for accuracy and precision, you will need someone in the surveying profession to help.

 

[jaja6009]

You can sometimes find very high resolution orthomaps from your county GIS department. My county has maps with a GSD that sometimes gets down to 1 foot (Made from an airplane using Eagle view Pictometry). You could use this data for some decent 2D GCPs. You basically find items in the images and get the latitude/longitude of the corners of the items or centers of objects and use these as GCPs. Keep in mind though that this will not get you "survey grade" control points. You are using data with a GSD of 1 foot and up to begin with, adding in the loss of accuracy of then marking them.

You could also look for free state LIDAR data and do the same and this would allow for 3D GCPs. This workflow would have similar accuracy/precision as above and all depends on the accuracy/precision of the LIDAR data being used as well as how dense the LIDAR point cloud is as a thin cloud would make it very hard to find the objects an thus losing more accuracy.

Both options above represent getting ballpark absolute accuracy and would be a decent way to get maps to overlay each other in the same area. But these methods are not acceptable if you want to try to acheive "survey grade" data.

From your other thread I see you have a M3E. Take advantage of the RTK by receiving corrections to the drone from either a personal base (DJI DRTK or Emlid Reach) setup on a known point or by receiving corrections from a paid service or a free state DOT service. But you will still need a handheld rover to measure checkpoints to "check" the accuracy. Emlid RS2 or 3 work great for this purpose.

My Sample workflow
Receive corrections from NTRIP RTK service to my drone and my handheld rover (Emlid RS2)
Measure control points in the area to be mapped. I use checker board targets easily seen from even 300' AGL.
FLy mission with drone receiving corrections.
Use the measured control points as only check points, but I usually measure extra control points that can be used as Ground Control Points, just in case I do not achieve my desired absolute accuracy with my check points. But in almost all cases so far, I have not needed the ground control points.
Long baselines (< 20km) from a services Base/CORS will entail a change in workflow by switching to PPK or setting up my Emlid RS2 as a local base on either an NGS monument or my own known point that has been logged for 6 to 12 hours and run using OPUS or PPK.