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Author Topic: Microdem "grid is too large error"  (Read 5357 times)

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_AUS_Salmo

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Microdem "grid is too large error"
« on: April 27, 2010, 03:35:41 AM »

Please forgive my posting in the Lounge. This post should be made in the MapWorkz forum but 'for some reason I don't have a new topic button available there.

I'm making a new map using satelite elevation data & microdem. I can merge several DEM files into one file, but the problem I have is that I hit a Microdem limit where I cannot merge any more DEM files (grid is too large error). Is there a way to overcome this error and stitch more DEM's together?
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_AUS_Salmo

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Re: Microdem "grid is too large error"
« Reply #1 on: May 03, 2010, 06:17:52 PM »

What? No map makers out there?  ::)
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farang65

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Re: Microdem "grid is too large error"
« Reply #2 on: May 04, 2010, 12:37:21 AM »

A map in the FMB can only have so much in memory size for it to handle.

if you have a map that is way to large you'll probably have to split it.

I think from my knowledge a Mymap_c should really be up to 75mb in size.
(Correct me if I am wrong)
If your Mymap_c is over like around 120 mb in size it will have memory load problems in the FMB.
It may load up fine in your map making version but it will have probs in the FMB.
Take Fabian Fred's Upper and Lower Burma maps.
He initially made one Burma map but it was too large in memory size so he split the map in to two Upper and Lower Burma.

I hope that helps.

I've never seen away around this situation in Microdem.

I've come across this as well and I just slowly crop the DEM down to suit the maximum size for Microdem.

Cheers Kirby
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agracier

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Re: Microdem "grid is too large error"
« Reply #3 on: May 04, 2010, 01:12:36 AM »

I'm making a new map using satelite elevation data & microdem. I can merge several DEM files into one file, but the problem I have is that I hit a Microdem limit where I cannot merge any more DEM files (grid is too large error). Is there a way to overcome this error and stitch more DEM's together?

If you have already merged a number of strm tiff files together to make a DEM, then the resulting DEM should already be quite huge for an Il-2 map ... far too large to ever load in the FMB.

Unless perhaps you are working to a very small scale, not 1/1, but 1/3 size or 1/4 or whatever.

You can overcome this by making 2 somewhat overlapping DEMS and then creating the 2 corresponding sets of color and gray bmp files. These two sets are then merged/stitched in a graphics editor to cover whatever area you wish. The stitching has to be pixel perfect unless you want to have some weird landscape flukes show up, but otherwise it's straightforward after that.

Otherwise you can vary the number in Microdem when you put in the 'set map pixel size' command. Instead of using 50, which gives a 1/1 scale, use a higher number, 100 for instance should give you a much smaller resulting set of color/gray bmps which should then not give any memory problems for processing ...
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_AUS_Salmo

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Re: Microdem "grid is too large error"
« Reply #4 on: May 04, 2010, 06:27:33 AM »

Thanks for the replies. I'm aiming for a 1/2 scale (1:2) map. I'm loading & merging raw DEM files. I have two raw merged DEM's that load within Microdem's memory constraints. Raw DEM pixel size is 780 & I've been trying to scale this to 1560 (yes, I know that's a large area), but the two large dem's merged still give a "grid too large" error.

Should I be using pixel = 100 to 1/2 scale the 2 dems then try to merge them? Any other techniques?
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agracier

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Re: Microdem "grid is too large error"
« Reply #5 on: May 04, 2010, 06:45:50 AM »

Thanks for the replies. I'm aiming for a 1/2 scale (1:2) map. I'm loading & merging raw DEM files. I have two raw merged DEM's that load within Microdem's memory constraints. Raw DEM pixel size is 780 & I've been trying to scale this to 1560 (yes, I know that's a large area), but the two large dem's merged still give a "grid too large" error.

Should I be using pixel = 100 to 1/2 scale the 2 dems then try to merge them? Any other techniques?

If you have trouble merging these files in Microdem, then why not create the color and gray bmb images, for each single DEM and then, in a normal graphics editor (GIMP, Photoshop, Paint Shop pro or whichever), merge the two sets of bmp files together? Stitch gray1 bmp and gray2 bmp into one larger full sized gray bmp?

This will work much easier than fooling around with Microdem. Don't bother too much with MIcrodem except for what is strictly necessary.

In fact, as long as you are careful with stitching/merging bmp files, then you can do this with 2, 3, 4 or more sets ... but in a normal graphics editor.

When you merge or stitch the two sets together, just be sure they are aligned pixel perfect in both color and gray.
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farang65

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Re: Microdem "grid is too large error"
« Reply #6 on: May 04, 2010, 09:03:11 PM »

This is something else I do if your DEM exceeds memory if you try 50 pixals and you get a pure white image.

I use Clock Watcher's method to make

Mymap_c, map_h and map_T

If you first crop your dem some and iput in 50 pixals and you get a white screen and a message saying you need this size or your dem exceeds memory this is what I do.

I first make .bmp images in microdem using Clock Watcher's method.

map_h is 200 pixals
map_T is 200 pixals.

There are two methods for Mymap_c

If it is a reasonably small map you can easily make a Mymap_c with 50 pixels but you'll have to blur the image a couple of times to get nice shore line edges.

If it is a large map I make Mymap_c as 200 pixels at first.

Mymap_c  200 pixels bmp       Microdem image
map_h     200  pixels bmp      Microdem image
map_T     200    pixels bmp   Microdem image

I then crop the three bmp images in multiples of 32 they will naturally all be the same size.
I change the photos to grey scale etc. and change to a .tga file after I have cropped the photos.

map_h and map_T are 4 times smaller than Mymap_c.

I scale down map_h and Map_t to suit this dividing by 4 My map_c w and h.

Doing this gives your Mymap_c  image automatic anti aliased edges. You don't have to blur the image as you have to if your Mymap_c is in 50 pixals.

Your ed map images are based on your Mymap_c image size and you crop this image the same size as Mymap_c then you scale down by half for the second ed map then again by half for the third ed map.

The third ed map should be the same size of map_h and map_T


Cheers Kirby

I use this method a lot and it works well.

Cheers Kirby
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_AUS_Salmo

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Re: Microdem "grid is too large error"
« Reply #7 on: May 05, 2010, 03:04:01 AM »

Once again, thankyou guys for the detailed information. This is what I was looking for. Now I'm off to give it a go :)
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agracier

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Re: Microdem "grid is too large error"
« Reply #8 on: May 05, 2010, 03:13:32 AM »

I use Clock Watcher's method to make

Darn ... this sounds very useful. I will have to keep this in mind. Never thought to start with the smallest size maps and work upwards.

The color maps are relatively unimportant anyway, since overlays from other sites are more colorful. And my_mapc needs blurring anyway.

The only hiccup I would think, might be making intricate river systems. There's a lot of good info on landscape if you make a full sized 50m gray map and you can easily see many rivers ... and sometimes it's useful to extract height areas from specific locations to help in placing fields or other textures. A full sized gray map gives more info ...

But still ... I'll give it a try as well ... thanks for the info ...
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farang65

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Re: Microdem "grid is too large error"
« Reply #9 on: May 05, 2010, 04:08:56 AM »

Hi Agracier

When your making Mymap_c in Microdem make sure lakes and rivers are ticked
in the big reflectance box, Azimuth 0 change water colour to black and check gray in the colours list I think 4 boxes you will see but just check grays.

Your Mymap_c should have black ocean grey land areas and black rivers and lakes.

You then use threshold in a photo program to change the gray to white as in a normal Mymap_c

Your rivers and lakes will come out reasonably well on a Mymap_c in Microdem.
Some will also show as black dots (connect the dots on a template and you have a river).

However they do need to be adjusted with a rivers template like you usually do.
Some can be broken in places.

I just made a map of Trinidad and Tobago with a massively large river system in
Venezuela. This system came out ok but needs some detailing work on a template.
At least it gives you half a chance with rivers at the beginning of a project.

And back to the height of water that can be done from what you suggested for map_h in another thread.

Here's a Mymap_c which has been made in Microdem and finalized in Gimp.
You can see some river systems and a huge lake.
You can also see some faint outlined rivers and connect the dot style rivers



Cheers Kirby
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