Geo-referenced TIFF images

Discussion of MicroSurvey CAD related issues and questions.

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Joined: Tue Mar 25, 2003 9:49 am

Geo-referenced TIFF images

Post by rschnei3 » Fri Mar 28, 2003 1:20 pm

I'm having problems gettting my GEO-tiff images imported properly into Micorsurvey..I am able to import the same file into Microstation/J and ArcView and it comes in with the correct size and coordinate values with minimal's what I know about this tiff image:

1) I have the accompanying tiff world file...from that I know the coordinates of the world tie point (which is the "world" coordinates for the lower left hand corner of the image which are x=836653.586, y=505195.0926 and the datum is the Wisconsin County Coordinate System, Dane Zone)

2) I know that this image has a ground resolution of 6" per pixel. Further I know that the image has physical dimensions of 11243x11240 pixels (156.15x156.11 inches)....according to my imaging program the image has a resolution of 72dpi. In addition, the image covers rougly 1/4 of a section.

Here's what I know about my Microsurvey file:

1) When I initially setup my Microsurvey file to import my survey data, in the General Configuration Options, I set the drawing scale factor to 1.

What we can't get a handle on is the scale to use when importing this image...when we use what we feel should be the correct scale, the image comes in too small.....when we manipulate the scale to fit the surveyed data (which we know is correct), we come up with a scale that doesn't seem to make sense for the image....

Another interesting thing we run across occasionally when unloading the image is the following error message (which is in German???)

*FATAL*: kann Datei 'e:\raster\s81028ibd9.tif.gri' nicht zum Schreiben öffnen.

Glen Cameron
Posts: 1395
Joined: Fri Nov 08, 2002 12:18 pm
Location: Corbeil, Ontario, Canada


Post by Glen Cameron » Fri Mar 28, 2003 10:38 pm

We do not support or use the World File that you have at your disposal.
The Drawing scale that you set when you first start a job has nothing to do with the raster image. It is there for when you place text and symbols, so we can determine the correct height of Leroy text for you and maintain a consistent size for symbols placed via our AutoMAP routines for all your drawings.

I just inserted an RLC raster image into my drawing.
It was scanned at 75dpi. The original scale of the paper drawing was 1"=1600'. In the raster dialog I enter in 75 dpi and a scale of 1600. There is a button marked < that allows me to pick the insertion location in the drawing on screen or I can manually type in the desired location. This is not geo-referenced and you may have to move the image to get it to the desired location. It is based upon the bottom left of the raster image but may be off a bit (mine was). The Rotation is counter clockwise as a positive degree.decimal degree angle. The color only affects RLC images as they are Black and White by default and this option can supply a color to them. TIF and BMP files come in with the color, as they were saved.

If I then measure the distance in the drawing on the scale bar it measures as 133.3 in this case which is 1600/12 (we measure in feet as whole units, and with 12" in a foot, this works out correct, or close enough for scanned images).

The Raster program is written in Germany and yes the messages those raster routines output are in German.

Roughly translated, the message you have quoted says: It can't open the GRI file for writing.

The GRI file contains information similar to this:
479 # lines
600 # cols
3769.0434 # x0
4430.1286 # y0
25.4000 # scale
400.0 # dpi
1 # color
0.000000 # rotation

And appears to be created for TIF and BMP files only, not RLC files.
I hope this helps!

Glen W. Cameron, C.E.T.
City of North Bay, Ontario

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