Removing/changing geo-referenced information embedded within an image.
mtm815
Global Mapper UserTrusted User
I wondering how to remove embedded geo-referenced information from an image. I can easily load the image into GM, however I think it may be geo-referenced incorrectly. I'm trying to rectify the image to a landgrid opened in my project, but once I do the image was no longer visible. Also, I had to change the projection from UTM to Geo-lat/long. When I export the image to GE, it places the image in the ocean. Do you have any suggestions?
Thanks,
Michael
Thanks,
Michael
Comments
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Hello Michael,
We will be able to provide a suitable response with a little more information from you.
For example using your previous ASC file, open the Overlay Control Center, select this layer and click on the Metadata button at the bottom, then use the "Copy to Clipboard" button and paste the results in your next post. This information should look like this:
FILENAME=C:\Users\<my name>\Downloads\GGX Well Spots.ASC
DESCRIPTION=GGX Well Spots.ASC
AREA COUNT=0
LINE COUNT=0
POINT COUNT=4504
UPPER LEFT X=1236629.04
UPPER LEFT Y=638898.84
LOWER RIGHT X=1398987.70
LOWER RIGHT Y=473402.19
WEST LONGITUDE=100° 0.08986' W
NORTH LATITUDE=33° 24.44086' N
EAST LONGITUDE=99° 27.56937' W
SOUTH LATITUDE=32° 56.58516' N
PROJ_DESC=State Plane (Texas North Central) / NAD27 / feet
PROJ_DATUM=NAD27
PROJ_UNITS=feet
EPSG_CODE=32038
COVERED AREA=963.82 sq mi
Now load your image using the settings provided in the file. Again, select the layer for this image in the Control Center, and paste the Metadata information in your post. You should not have to change anything at this point, if the georeferencing data in your image is complete.
You have already said that you want to use NAD-27 UTM for your project, so we can use that information unless it has changed.
This will provide enough information for us to see where you are, and where you want to be. I'm sure we'll have more questions, but this will help us get started more quickly.
Thanks,
Mykle -
Michael/Mykle,
What you might also do if you want to just completely ignore any referencing built-in to the imagery and reference it against something else is first load your reference data, then load the data you want to reposition with the File->Rectify Imagery menu command. Then enter control points (probably 4 or 5 if possible) by clicking them on the reference image and the image to position and adding control points, then press OK to complete the rectification. Note if your image is likely projected and not raw lat/lon you might want to first change the projection on the rectification dialog to a UTM projection that covers your area of interest. That usually works for most types of maps covering relatively small areas.
Let me know if I can be of further assistance.
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Global Mapper -
Mykle,
Here's the Metadata for the landgrid. The projection/zone/datum is State Plane/Texas North-Central/NAD-27
FILENAME=HASKELL_SURVEY.CDF (C:\Users\mmowrey\Desktop\Documents\Work\Projects\Texas\Haskell County\Geospartial\Whitestar\HASKELL_SURVEY.zip)
DESCRIPTION=HASKELL_SURVEY.CDF
AREA COUNT=2616
AREA VERTEX COUNT=22238
LINE COUNT=0
POINT COUNT=2744
UPPER LEFT X=-99.99
UPPER LEFT Y=33.40
LOWER RIGHT X=-99.47
LOWER RIGHT Y=32.96
WEST LONGITUDE=103° 55' 9.4019" W
NORTH LATITUDE=31° 29' 55.5104" N
EAST LONGITUDE=103° 55' 9.3956" W
SOUTH LATITUDE=31° 29' 55.5057" N
PROJ_DESC=State Plane (Texas North Central) / NAD27 / feet
PROJ_DATUM=NAD27
PROJ_UNITS=feet
EPSG_CODE=32038
COVERED AREA=0 sq mi
Here is the metadata for the image. The Projection/Zone/Datum is UTM/Zone 14/ NAD-83
FILENAME=C:\Users\mmowrey\Desktop\Documents\Work\Projects\Texas\Haskell County\Images\Aerial Photos\East Stu Prospect\Aerial Photo 1953\02-5-1954_674.tif
DESCRIPTION=02-5-1954_674.tif
UPPER LEFT X=0.000
UPPER LEFT Y=8.298
LOWER RIGHT X=9.205
LOWER RIGHT Y=0.000
WEST LONGITUDE=103° 29' 18.0348" W
NORTH LATITUDE=0° 00' 5.4438" S
EAST LONGITUDE=103° 29' 17.7074" W
SOUTH LATITUDE=0° 00' 5.7475" S
PROJ_DESC=UTM Zone 14 / NAD83 / meters
PROJ_DATUM=NAD83
PROJ_UNITS=meters
EPSG_CODE=26914
COVERED AREA=0.0000295 sq mi
NUM COLUMNS=9205
NUM ROWS=8298
NUM BANDS=1
PIXEL WIDTH=0.001 meters
PIXEL HEIGHT=0.001 meters
BIT DEPTH=8
SAMPLE TYPE=Unsigned 8-bit Integer
DPI=1000
TIME=2013:04:04 10:01:53
GT_CITATION=PCS Name = NAD_1983_UTM_Zone_14N
GEOG_CITATION=GCS_North_American_1983
PHOTOMETRIC=Greyscale (Min is Black)
BIT_DEPTH=8
SAMPLE_FORMAT=Unknown Format (0)
ROWS_PER_STRIP=1
COMPRESSION=None
DPI=1000
PIXEL_SCALE=( 0.001, 0.001, 1 )
TIEPOINTS=( 0.00, 0.00, 0.00 ) --> ( 0.000, 8.298, 0.000 )
MODEL_TYPE=Projection Coordinate System
RASTER_TYPE=Pixel is Area
OVERVIEW 1=Pixel Size: 1314 x 1185
I have tried rectifying the image to the landgrid with no success (I changed the projection of the image to 'State Plane ect...' before rectifying). After rectifying the image to the grid it becomes invisible. When I push the full extents button (to see if the image is off screen somewhere) the extents do not change, as if the image has been rectified correctly.
Additionally, when I just import the image by itself into a new project it shows up. But when I export the image (without changing the projection or embedded geo-referenced information) into GE, it places the image in the middle of the ocean, which makes me think that the geo-referenced information is bad...
Thanks for the help. Hopefully this gives you enough to work with.
Michael -
The following lines are the native bounds for the TIFF:
UPPER LEFT X=0.000
UPPER LEFT Y=8.298
LOWER RIGHT X=9.205
LOWER RIGHT Y=0.000
Those are clear not correct, if lat/lon they would be near the equator and prime meridian. So just ignore whatever is in the file and load it with File->Rectify Imagery and provide completely new control points to tie the TIF to the existing land grid that is properly placed. Just a few common control points should do the trick.
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Global Mapper -
The following lines are the native bounds for the TIFF:
UPPER LEFT X=0.000
UPPER LEFT Y=8.298
LOWER RIGHT X=9.205
LOWER RIGHT Y=0.000
Those are clear not correct, if lat/lon they would be near the equator and prime meridian. So just ignore whatever is in the file and load it with File->Rectify Imagery and provide completely new control points to tie the TIF to the existing land grid that is properly placed. Just a few common control points should do the trick.
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Global Mapper -
Michael,
There are many files (mostly GeoTIFF and DXF in my experience) that appear to have incorrect information and require manual rectification. This might be expected for a few files, but many of these appear to come from what should be reputable sources, or exported from well-known programs. So I wonder whether other programs make assumptions that allow the files to be properly used. That would certainly make life difficult for Mike and Global Mapper, and therefore complicate our lives.
I frequently need to find some other information so that files can be properly registered. That can be a difficult task when points on the image are difficult to relate to points on other layers.
A pet peeve is clients that give us a Google Earth screen capture, when the view is not vertical, and when the vertical exaggeration is not as small as possible (currently the free viewer is limited to a minimum of 0.01). Not Good. But I digress ...
Mike has pointed out that the native bounds in your image file are not correct. The values are simply using the NUM COLUMNS times the PIXEL WIDTH, and NUM ROWS times the PIXEL HEIGHT, and implying that your image covers 8x9 meters. These values should contain the coordinates of the upper left and lower right corners of the image.
The coordinates have a longitude that looks okay, until you notice that 103W is in New Mexico.
As Mike suggests, this image will require manual rectification. You will probably find this to be easier by specifying (in the rectification dialog) UTM Zone 14 / NAD83 / meters. If you have points on other layers that you can identify in the image, it will be a simple task.
Use your data points if they accurately relate to what you can see on your image. My impression with a quick look was that they would not be useful for rectifying the image.
You may need to be satisfied with less accurate methods, like finding a point on your image that is also in Google Earth, and transferring the coordinates (set Google Earth to display UTM coordinates in this case). A road intersection would be good. I have used high power lines when I can see the towers in both images. If your imagery is really from 1954, be careful of changes that have been made since then. Sometimes the Google Earth historical imagery can be helpful.
Mykle
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