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Guest luissa

Aligning the map!

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Evening all,I've now began work on my English Lake District (south) project. Well, at least I'm trying to align my map correctly in ground2k4.I use a grid reference -> lat/long coverter to place the northwest and southeast points correctly on the map. My problem is with map rotation. Because my new map has a much larger east-west coverage than my old projects, there's a large variation in the true north deviations on the map.For example, the western section of the map has a deviation between grid north and true north of 1.02 degrees. The eastern section has a deviation of 0.41 degrees. So in Adobe Photoshop, I rotate the map by varying degress between these two published deviations.I restart a new LVM project after each rotation, using fsconnect I can see how well matched the map is to the location of my plane at Walney Island airfield, Barrow. The result is that the fs2004 runway is 0.5km to the south of the runway on the map. This airfield is located in the south western part of the map - the furthest distance from the two fixes - and the only fs2004 airfield on the map.So, it seems that whatever I do will be a fudge regarding alignment. Is there a way of 'warping' the map so that 'up' points towards True North at all points on the map?Any suggestions welcome.Anthony Dyer

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Hi Anthony,I suggest you use some kind of GIS software (Geographical Information Something... hem.) to "rectify" your map. I would recommend *GlobalMapper* which is a low-cost while very powerful software. You can download a -limited- free version on their site.It reads formats such as (Geo)Tiff or PNG as input - scanned maps, satellite data for instance - then asks you to rectify it manually. To achieve this you just have to know the precise coordinates of two points (at least, the most points you enter the better the result is). Choose the desired projection type, according to the desired result and the kind of coordinates you entered. Then watch the algorithms deform your map, stretch it, rotate it... :)Finally you have options to export the resulting image (or part of it by entering boundary coordinates) as a Tiff file. Any good imagery software will then convert it to Bmp, Png or whatever usable format.I use it for several months now, it has lots of useful functions (such as overlaying several inputs e.g. satellite data over scanned map, editing palettes...). After a few days/weeks of learning, I was able to get very precise results under FS ! :)Hope it helps,(forgive me for my bad English)HotShot

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Howdy,HotShot's suggestion is definitely the ideal thing to do. But even if you don't end up purchasing GlobalMapper you can use the demo version (which doesn't allow exporting) to change the projection of your source image and then take screenshots of the correctly projected image. If the area is fairly large, you'd have to patch the screenshots back together in Photoshop but it beats trying to "warp" the source image itself.Another thing to be aware of is that many of the smaller airfields in FS are not quite in the correct position. Even if your image is projected correctly it still may not align with the airfield(s). In that case you'd have to either asjust the image position or re-make the airfield in the correct postion.Cheers, Holger

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Thanks for the suggestions. I'll certainly give global mapper a go (is it a download size my dialup can cope with?). I've noted that airfields can be out of line, but I've discovered that mountains are probably better reference points than airfields - particularly with the lago terramesh I'm using. Deviations are fairly small near the NW & SE fixes but between 300 - 400metres when we get away from the fix points.Unfortunately I've already started placing my rivers & coasts down. While I'm able to realign the rivers to fit in the valleys (and not half way up a slope) - it's laborious. Once a project is started I don't seem to be able to recalibrate the map in ground2k4. Are there any workarounds to this without deleting & restarting a project file (entries in the source code)?

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It is 8 Mb in size. And the demo version should be sufficient if you don't have to deal with enormous areas as Holger said. :)For your already started project it is actually a matter of style. What kind of perfectionist are you ? ;)

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Howdy,"Once a project is started I don't seem to be able to recalibrate the map in ground2k4. Are there any workarounds to this without deleting & restarting a project file (entries in the source code)?"As long as the source dimensions of the background bitmap don't change (i.e., columns and rows) you can safely adjust the image coordinates in the "Parameters > Coordinates of the Map" window. I once had a project misplaced by a couple hundred meters and just shifted it this way without problems.Cheers, Holger

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>It is 8 Mb in size. And the demo version should be sufficient>if you don't have to deal with enormous areas as Holger said.This is the business! Shame they're wanting $179 for it. I assume you just do a bit of "Print Scrn"'ing. There seem to be other GIS manipulation tools. Do others export images for free? The thought of going through hundreds of print screens doesn't appeal.http://www.gisdevelopment.net/downloads/gis/> What kind of perfectionist are you ? ;)I'm an iterative perfectionist :-)Anthony Dyer

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Hi Anthony,Actually, $179 is a bargain for a GIS (though, technically, Global Mapper is not really a full-fledged GIS). I use Idrisi, and that's considered "low cost" at US$900, ArcInfo is close to $10,000 per license!Another option, Manifold GIS - http://www.manifold.net/products/mfd50pro/mfd50pro_home.html - used and praised by Justin of FS Genesis, is about US$300. It's possible that there is some freeware reprojection software out there somewhere but I've never come across any. Actually, there is one: GRASS GIS - http://grass.baylor.edu/ - but it's not exactly an easy tool to use (or, at least, used to be when I worked with it on a research project about four years ago). In general, for free tools and data, this site is probably a good start: http://software.geocomm.com/index.htmlCheers, Holger

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