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Eastings and Northings

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#1
TCMail

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Hello all,

My work involves plotting airfields around the world, and we use Avenza MaPublisher to create our own co-ordinate systems for the specific area of interest.
We currently use an outside program to obtain the latitude of origin and the central meridian, as well as eastings and northings. This computer program is about to be made obselete and my company has not worked out how to move forward from it.

Through experience with the program we can make out that the above data is simply the same as the airfield centre point, but we do not know how to calculate the eastings and northings. They also seem to be referred to as false. For the airfields we already have, the data does not match up with for example the Google Earth data, so its not quite that simple.

I wondered if anybody has experience of using MaPublisher this way, and if they could help us.

Many Thanks
TCMail, London, UK

#2
Sab

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Some GIS packages allow you to have projection on the fly, which reprojects the vector/raster data to the canvas projection.

For example in QGIS which can handle projection on the fly for vectors and rasters:
You can set the canvas projection to WGS84 (EPSG:4326) and allow the projection OTF.
Then you can add data from British National Grid (EPSG: 27700) or your own custom projection. They will all appear as lat/long.

If you want to add google maps or other basemaps, you can use Google Mercator (EPSG:900913) for your projection OTF.
Some useful links:
http://www.qgis.org/wiki/Download
http://spatialreference.org/

#3
Michael Schmeling

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A false easting or northing is simply an (arbitrary) offset to the true north or east value. They are mainly used to avoid negative numbers in the coordinates. For UTM projections these false eastings are predefined for each UTM zone. You need to figure out what offset is used by your program. For example, take a point at Lat/Lon 0,0 and find out out what coordinate it is given by your program. What projection is used by this program?
Michael Schmeling
Kassel, Germany
Arid Ocean Map Illustrations
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#4
TCMail

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We use Adobe Illustrator with the MaPublisher addon to plot our points, mainly because we then use Illustrator as a drawing program.
MaPublisher uses a transmercator, and basically what we are doing is changing the central meridian, latitude of origin, and the false easting and northing within mapublisher to our own values.

#5
Sab

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You need to use a proper GIS (i.e. QGIS :)) and export your graphics to SVG

#6
David Medeiros

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MAPublisher is a 'proper GIS', it just focuses on cartographic output rather than statistical analysis. And it handles projections and transformations with ease. My guess is the PO would have the same issue in Arc, QGIS or MAPub.

Arid Ocean explained the set up pretty well. It may help to serve up a couple of existing files for inspection if possible. Without having seen exactly what you are doing it sounds like you just need to determine the existing offsets (the false eastings and norhtings) from older files and see if they are constant. If so you probably only need to determine Lat/Long of the new airfield center point to get your central meridian and lat of origin then add the false offsets.

I'm not in front of MAPub right now so take with a grain of salt. More info and some files to open up would help.

GIS Reference and Instruction Specialist, Stanford Geospatial Center.

 

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