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LaurieM
12th December 2009, 06:01 PM
G'day.

I have two map making programmes: TatukGIS and ElShalel.

I download the data from Geoscience and make the map in TatukGIS. Works fine except for one little problem that I haven't been able to get to the bottom of.

The map is distorted. That is, stretched about 10% on the horizontal axis and compressed about 10% on the vertical axis.

When I use the measure tool on the programme it records this error and when I measure it on the screen with a ruler it's there.

If I save and print a map the error is still there.

But if I put a saved map into OziExplorer it comes correct.

It happens with both programmes. I use TatukGIS because it took me a lot to learn it and I'm sticking to what I know, if possible.

Any idea why the map distorts? I know I haven't given much information to go on. Would be happy to give more info if I knew what was needed. ;)

Thanks,

The Explorer
12th December 2009, 06:11 PM
Hello
Probably something to do with the projection being used to display the map (lat/long, UTM ect, ie method used to display ~spherical earth on a flat map). You will get distance measurement issues with some programs that dont take into account projection. OziExplorer is pretty good at it so that may explain good result there.

Cheers
Greg

LaurieM
13th December 2009, 02:09 PM
Thanks Greg.


Probably something to do with the projection being used to display the map (lat/long, UTM ect, ie method used to display ~spherical earth on a flat map).

Yes, the Tatuk programme that I have is the viewer which they give away free. The other part is the editor and you'd buy half a dozen OziExplorers for one Tatuk. So I think it's more likely that I have something set up wrong; something that I don't understand (and there's plenty of that). Maybe what I need is in the editor, but I have no plans to buy it.

The other programme, ElShalel, has some stuff about changing from one thing to the other but it's beyond me.

It's really quite unfortunate because I'm only just a bee's whisker away from producing good quality paper maps with the features that I want.

For my next trip I want to join four or five map sheets to take in part of the Flinders Ranges and west of Lake Torrens up to Lake Eyre South.

If you've been out in that country you'll understand what it's like, traveling on a motorbike, trying to read a paper map with flies crawling up ya nose and in ya eyes while the wind is blowing the map around and there's so much glare that ya can't see anyway. No shade, no windbreak!

So I want to print the maps in A4 sections and have them in a folder.

I guess the other question is:
Are those $150 GPS any good? I see one on eBay for $120, the other day.

I have my Garmine Etrex (no maps) as a backup. Maybe a moving map would be the go. Check out the paper map in the tent before I start in the morning and use the moving map.

The Explorer
13th December 2009, 02:31 PM
snip

It's really quite unfortunate because I'm only just a bee's whisker away from producing good quality paper maps with the features that I want.



Can you provide small example (ie zip and attach to post). Is their some setting for projection when you are creating the map? Do you know what projection is being used?


snip

If you've been out in that country you'll understand what it's like, traveling on a motorbike, trying to read a paper map with flies crawling up ya nose and in ya eyes while the wind is blowing the map around and there's so much glare that ya can't see anyway. No shade, no windbreak!



Yes I understand - exploration geo/field zoologist for 20 years, plus done a few Aus Safaris on Motorcycle.


snip

I guess the other question is:
Are those $150 GPS any good? I see one on eBay for $120, the other day.



No idea - dont know which one your talking about. Suspect they may not be that reliable on a motorcycle though..but for $120 maybe worth a bash - assume you want to run OziExplorerCe? It is possible to run OziCe on some Magellan Triton GPS units with a unlock program...or the standard unit will display raster topo maps in a RMP format - free raster converter on the net. It is also possible to display small raster maps on Garmin Oregons now....and then of course there's the Aventura but a tad expensive considering at the beginning of this paragraph we started off at $120 :).

Cheers
Greg

LaurieM
13th December 2009, 06:25 PM
OK. Here's a fragment of a saved map. It was the first one I found. It was a BMP because I have only the free version of OziExplorer which will take only BMP.

Well, I've tried to attach the map. Don't understand how this forum works. The VB attachment is different to another VB I'm on.

This map doesn't have many features but I can add all I want to the version in TatuckGIS: roads, water points, sand dunes, spot elevations, place names, whatever. Change the colours and line width. The maps really are as good as bought ones except for the one hassle.

Ya know, as long as I say the problem isn't with the programme, but with my understanding, I'm in control and have a chance of getting it right. Blaming the programme or the data doesn't help.

LaurieM
13th December 2009, 06:43 PM
Try again. Put the image on my spare blog.


Andamooka Island, Lake Torrens, South Australia

http://www.southimage.net/digital-images/wp-content/uploads/2009/12/map_01.jpg

LaurieM
13th December 2009, 07:18 PM
Here's a screen shot from the ElShayal programme. Is this what I'm looking for?


Lake Eucumbene

http://www.southimage.net/digital-images/wp-content/uploads/2009/12/map_02.jpg

The Explorer
13th December 2009, 07:26 PM
Hi
Yes..as suspected the maps you are producing are using a geodetic - lat/long projection. To be able to print out and use in the field for measuring distance using metres as a scale the maps will need to use TM or UTM projection. I calibrated the image you posted and reprojected to UTM. As you can see the grid lines now form "proper" 10km squares.

So...look in the settings of the program you are using to make the maps to see if you can use UTM pojection.

The Explorer
13th December 2009, 07:29 PM
Here's a screen shot from the ElShayal programme. Is this what I'm looking for?



The coordinate system in this case seems to refer to the datum...not the projection. Your problem relates to projection so changing the datum wont help.

Cheers
Greg

LaurieM
14th December 2009, 08:19 AM
OK, thanks. Been doing my homework.

Here's a bit from the TatukGIS tutorial:


Tutorial 10 - Measurement Tools
Previous Top Next

The Viewer provides two ways to measure length/distance or the areas and perimeters of areas. One method calculates these measurements based on an already existing vector in an open layer. The second method calculates these measurements from a temporary line or polygon which is drawn on top of the other map layers.

The map layer(s) must be in a projected coordinate system, with linear units (meters, feet, etc.), for the measurement to yield accurate results, because the measurement results are presented in the same units as the units used by the coordinate system. If, for example, the measurement were performed on a layer defined in longitude/latitude coordinates, such as the common WGS84 coordinate system, the measurement results will also be provided in coordinates, which is not meaningful.

Here are the grids and graticules from TatukGIS. Same in ElShayal. This must be telling us something, but I don't understand enough to know what it is. ;)


Grids

http://www.southimage.net/digital-images/wp-content/uploads/2009/12/grids.JPG

Graticules

http://www.southimage.net/digital-images/wp-content/uploads/2009/12/graticules.JPG

I can't find anywhere to change the projection. I guess it's how the data was made in the first place.

Thanks.

LaurieM
17th December 2009, 04:15 PM
Thanks for the help, Greg.

I've sort of got there. Well, sort of.

I've decided to simply ignore the converging grid. It's fine.

* I'll buy three more map sheets to complete the set I need for my trip. These will go in a tube in a box on the bike.

* I'll print copies of the map sheets at A3, derived from Geosience data. I did one practice map and although it's a bit small, these will be useful in a folder, easily accessible while traveling.

* I've installed the free version of OziExplorer on a laptop. Got a home made map and it looks to be calibrated correctly, though I'm not too sure about the last pair of coordinates shown in the image. Haven't yet hooked up the Garmine Etrex GPS.


OziExplorer on Laptop. Bottle Hill on Pernatty Station, SA.

http://www.southimage.net/digital-images/wp-content/uploads/2009/12/moving_map_01.jpg

John McDouall Stuart camped there on the night of 16 June 1858 and I camped there for two nights, a couple of years ago, too.



Wednesday, 16th June, Yolticourie. The horses have returned; they found no water last night; they were obliged to camp for the night, it being so dark, but they found Mr. Babbage's camp very early. The horses drank all the water. I was wrong in blaming the black fellow; he took us to the RIGHT Pernatta. It is another water that Mr. B. is encamped at. He moves to-day for the Elizabeth, which I also will do. He found the remains of poor Coulthard yesterday. We must have passed quite close to them in our search for water. He has sent for me to come and assist at the burial. It being so late in the day (12 o'clock), and the horses requiring more water, and he having four men besides himself, I do not see that I can be of any use, and it might cause me to lose another day, and the horses to be another night without water, which would be an injury to them, they not having had sufficient this morning. Mr. B. also sent to say that he would accompany me to the Elizabeth. I have delayed an hour for him, and he has not yet made his appearance; it being now 1 o'clock, and having to travel seventeen miles, I can wait no longer. Started for Bottle Hill; arrived on the south side of the hill an hour and a half before sundown, found some water and plenty of grass; encamped for the night. Distance to-day, seventeen miles. The former part of the journey was over very stony country; the latter part very heavy sand hills.


Thursday, 17th June, Bottle Hill. Got on the top of Bottle Hill to take bearings, but was disappointed; could see no hill except one, which was either Mount Deception or Mount North-west; the bearing was 51 degrees 30 minutes. There is a small cone of stones on the top, and a flat stone on the top of it, with the names of Louden and Burtt. From here I saw the gum trees in the Elizabeth; course to them 325 degrees 30 minutes, seven miles to the creek. The country from the hill here is of the very worst description--nothing but sand and salt bush.


Bottle Hill at Sunrise from My Camp

http://www.southimage.net/john-mcdouall-stuart/wp-content/uploads/2007/10/dsc_0415.jpg

There's a dam built on a swamp nearby, so I reckon this is the same view that Stuart awoke to, that morning.

Thanks again for the help.