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Author Topic: Problem generating coutour files for FL topo map  (Read 8663 times)

crunch

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Problem generating coutour files for FL topo map
« on: August 17, 2008, 03:17:35 PM »
I am following the tutorial to generate a FL topo map. I have a small problem with the data for the New Smyrna Beach quadrant (29.5 north, -81 west).  When generating the contour files for that quadrant Gobal Mapper chokes on the third ArcGrid file for that quadrant with a "Unknown error generating contours." error message.  I used the recommended values from the tutorial and a 1 arc degree for width and 0.5 arc degree for height.

That quadrant is a little strange, as only the first (west) data file holds land, the remaining three show only water.  I could reproduce the error using only the elevation data for that quadrant, and processing only the first two solves this problem.

I restarted the processing for all FL DEM files.  Lets hope there is no other problem, it took already a couple of hours to get to this problem and the progress bar only says 25%.

Is this a known problem, and does another workaround exist?

  Volker

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Re: Problem generating coutour files for FL topo map
« Reply #1 on: August 17, 2008, 04:17:28 PM »
I would not load the ones that just hold water because there wouldn't be contour data in those quads. This sounds like a problem with Global mapper.

I don't know of a workaround because I've yet to run into it.  I am pretty sure global mapper will read the tif files so perhaps download the tif for that quad and see what happens.  The tif will have just 1 file for the quad.

Let me know how that works for you and what happens.

Dan
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savage

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Re: Problem generating coutour files for FL topo map
« Reply #2 on: August 18, 2008, 03:46:34 AM »
I have seen those "Unknown error". It happens when you run out of memory(?). Try to reboot, unload everything you do not need (browser, mail, IM, etc.) and try again.

-Oz-

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Re: Problem generating coutour files for FL topo map
« Reply #3 on: August 18, 2008, 05:23:23 AM »
Yea, i just ran out of memory try to create the .mp segments for New Mexico.  less than a week and I'll have my new ram.
Dan Blomberg
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crunch

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Re: Problem generating coutour files for FL topo map
« Reply #4 on: August 18, 2008, 03:29:15 PM »
First I need to make a correction, I actually use 0.5x0.5 arc degree areas with 10ft distance between the lines, as Florida is supposedly very flat, for the contour calculations.  With 1.0x0.5 I run out of memory already in the second quad (Bay Minette).  Funnily enough the the error is something like: "Unable to save ...." (Sorry, cannot remember the exact text at the moment).

I did a comparison of the generated contour files for quad "Dothan":

With 1.0x0.5 arc degrees one gmp file with 336415767 bytes is generated, with 0.5x0.5 arc degrees two files with 13503542 + 14945378 = 28448920 are generated, so for some reason less bytes (10x less!!) are generated for the same area by only reducing the contour grid size.

Yes, maybe more memory would solve the problem, but that the areas with only water in them lead to problems hints at a problem in Global Mapper.  I had two more problems with "ocean only" elevation data and removing those areas seems to solve the problems so far.  Also, about how much more memory are we talking? My machine has 2GB plus virtual memory, as it is running on XP there is not much room for more (3GB usually, or 4GB with tweaks).

Volker

@savage: Maybe reducing the contour grid size solves your problem.

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Re: Problem generating coutour files for FL topo map
« Reply #5 on: August 18, 2008, 05:50:40 PM »
I have a few issues with my generation of hawaii too.  Wonder if its a global mapper bug;  I'd recommend contacting them and seeing what they say.

And 2gb of memory I would think would be enough with XP.
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savage

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Re: Problem generating coutour files for FL topo map
« Reply #6 on: August 21, 2008, 05:14:47 PM »
I am having a lot of troubles with Global Mapper and Maine. There are 4 or 5 quadrants that I cannot generate. I think I am seeing 2 different bugs.  One is the "Unknown Error" and the other bug is an infinite loop that seems to consume all the virtual memory.

twerp

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Re: Problem generating coutour files for FL topo map
« Reply #7 on: August 23, 2008, 09:05:27 AM »
HAVING THIS PROBLEM AS WELL WITH iDAHO. nOT SURE WHAT TO DO. cAN YOU FROM YOUR EXPERIENCE PROCESS CONTOUR DATA IN SMALLER CHUNKS. aLSO DO YOU JUST LET THE PROGRAM RUN TILL IT REACHS 100%. THIS COULD TAKE DAYS.

savage

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Re: Problem generating coutour files for FL topo map
« Reply #8 on: August 23, 2008, 09:37:08 AM »
I have not been able to work around this problem. I will contact Global Mapper soon about the issue. There is no need to let this thing run forever. On my machine I can process a quadrant (0.5 x 1.0) in less than 30 minutes. I have seen GM runs on some quadrants for more than 8 hours. My only work around is to use the FWTools to generate the missing quadrants. Actually FWTools works quite well.

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Re: Problem generating coutour files for FL topo map
« Reply #9 on: August 23, 2008, 09:17:40 PM »
fwtools is how my program processes it.

Maybe the download is no good for glab mapper; an error or something... try to download the quadrant again?
Dan Blomberg
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