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7 votes
Accepted

Difference between control point, reference point, and tie point

You can better understand the difference by taking a hypothetical drone/satellite survey example. So, in a drone survey, you collect multiple images and process them later. A tie point is the same ...
Yogesh Chavan's user avatar
3 votes
Accepted

Abnormal Output of OpenDroneMap with GCP file

The problem in its processing is that it is georeferencing all ground control points with the same elevation, when they clearly do not have the same elevation. The georeferencing process is not ...
Gabriel De Luca's user avatar
3 votes

Creating a GCP (*.points) file from a Shapefile (points layer)?

how do I create a GCP (.points) file? You could use a text editor. The format you want is like: mapX,mapY,pixelX,pixelY,enable 433268.37959376286016777,355509.77655098377726972,983.9774984446378312,...
nmtoken's user avatar
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2 votes
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Change project CRS = discard GCPs?

In most cases, the saved GCP file will be of no value. It works to georeference a raster that has no CRS, addressing pixels and lines. The usual workflow is to save the raster in a format that stores ...
AndreJ's user avatar
  • 76.8k
2 votes

Editing/adding GCPs using QGIS?

The process of adding and editing georeferenced points is doable within. Toggling editing of GCPs should allow you to select a GCP on either the map or on the img to reconfigure placement. Toggling ...
Robert Collins's user avatar
2 votes

Are all remote sensing landcover/use classifications without ground survey scientifically invalid?

It is very common for a published study to use the remotely sensed datasets as the reference data in validation instead of field data, especially when the study area is large (eg continental or global ...
TonyC's user avatar
  • 659
2 votes
Accepted

What does control points look like in viewer ? How spread do they need to be ?

Imagine your image is a flat piece of paper and you are trying to attach it to the surface of a spherical object with as little folds/wrinkles in the paper as possible by pressing push pins through ...
onakua's user avatar
  • 690
2 votes
Accepted

ArcGIS 10.5 - Testing the accuracy of a satellite image's georeferencing using dGPS ground control points

Basically, what you need is to compute the RMS of the positionning error. This type of analysis requires a manual input of points that you should place on your satellite image where you SEE that it ...
radouxju's user avatar
  • 49.8k
2 votes

What is the proper way to georeference an image based on GCP using GDAL tools

uou can use first gdal_translate to add GCPs to your image. I changed the pixel coordinates of GCPs to integer values (there is no much use of sub-pixel coordinates) gdal_translate -gcp 4 172 622077....
Zoltan's user avatar
  • 7,410
2 votes

Setting GCP in OpenDroneMap Project

If you set your project to hold images in /exam/ple/project/images then it's the /exam/ple/project (just one level up, this directory does not need to be called project) that you should put gcp_list....
Etua's user avatar
  • 21
1 vote
Accepted

How to give a coordinate to *.tif?

If you know the pixel size of the images (or the ground size of the image) then you can create a world file for the image. Line 1: A: pixel size in the x-direction in map units/pixel Line 2: D: ...
Ian Turton's user avatar
  • 82.2k
1 vote

Georeferencing Polygon Features using ArcGIS Pro

The vector equivalent to georeferencing of raster data is spatial adjustment. To do that in ArcGIS Pro see Is the Spatial Adjustment toolbar available in ArcGIS Pro?. That FAQ refers you to the ...
PolyGeo's user avatar
  • 65.2k
1 vote

GDAL GCP Transform - No GeoTransform() on GCP projected image?

Geotransform and ground control points are two different ways for defining the correlation between pixel coordinates and geographic coordinates. See https://gdal.org/user/raster_data_model.html GDAL ...
user30184's user avatar
  • 67.3k
1 vote
Accepted

How to georeference image with GCP in aux.xml using Affine transformation

Use gdalwarp https://gdal.org/programs/gdalwarp.html with -order 1 but instead of writing a new TIFF use VRT https://gdal.org/drivers/raster/vrt.html as outputformat. Command: gdalwarp -of VRT -order ...
user30184's user avatar
  • 67.3k
1 vote

Re-georeference an image that already has a spatial information

Already georeferenced image can be georeferenced with QGIS georeferencer without removing old georeference info first. However, georeferencer does not update the old image but it writes out a new ...
user30184's user avatar
  • 67.3k
1 vote
Accepted

Georeferencing a historic map to a local custom coordinate system

I would try to georeference it to EPSG:4326 and then change that to your local system. A 2-step process. Have you tried it?
wingnut's user avatar
  • 2,110
1 vote

QGIS custom coordinate reference system of a local site

Helmert transformation, intended for little angles, make the asumptiom that the cosine of a small angle is 1 and the sine of a small angle is the angle itself, in order to linearize the transformation ...
Gabriel De Luca's user avatar
1 vote
Accepted

Point Residual in photogrammetry

I don't know this specific software, but in photogrammetry each image will be adjusted according to the model that minimizes the square of the errors. The residual that is shown indicates how much ...
radouxju's user avatar
  • 49.8k
1 vote

Creating a GCP (*.points) file from a Shapefile (points layer)?

Like nmtoken said, you have to put them in a textfile similar to his example. It might be easy to use qgis to save the shapefile as a csv. Then you can open it in excel and change the layout according ...
Jan-Pieter's user avatar
1 vote

Is there a limit to the number of GCPs that can be used?

The error seems to come from the libtiff library, and the corresponding source code file is https://gitlab.com/libtiff/libtiff/-/blob/master/libtiff/tif_dirread.c So the answer to the question "...
user30184's user avatar
  • 67.3k
1 vote

Deleting GCP set in GEOTIFF?

By looking at the GDAL documentation https://www.gdal.org/classGDALDataset.html#ac91ea1fc26dd19f14d31baec4988d5b6 there are methods for setting ground control points and for reading a list of existing ...
user30184's user avatar
  • 67.3k
1 vote

Using gdallocationinfo on a rotated SAR image to get pixel value at coordinates

Okay, I found the cause of the problem. I got the order of the geotransformation parameters wrong. the georeferencing transform takes the following form : adfGeoTransform[0] /* top left x */ ...
Yardood's user avatar
  • 21
1 vote

Georeferencing CAD drawing and setting ground control points in GRASS?

Try using the Georeferencer in QGIS. This tool allows you to enter the control points by clicking on the CAD drawing and on the map canvas. It seems more user-friendly than the process you're trying ...
csk's user avatar
  • 24.9k
1 vote

Georeferencing X Y (AND Z) with GCPs in QGIS

I haven't found a solution directly in QGIS but with AgiSoft is possible to implement the solution which you are looking for!
Dieter Riedel's user avatar
1 vote
Accepted

How to apply control points in LiDAR?

You could always import the lidar data back into the software you used to initially process the point cloud and add the control points there. For example, this is a step that would be done in Leica ...
jwx's user avatar
  • 713
1 vote

Using PROJ.4 library to transform from local coordinate system coordinates to global coordinate system using ground control points?

I was stuck in the same problem a few weeks ago, I figured out a python script that can help. Original solution from here import pyproj import math import numpy as np from statistics import mean ...
Garth Cooper's user avatar

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