Hi,
I've not been able to come up with a comfortable way of handling projects with multiple coordinate systems in grass. Perhaps I'm missing something...
Our typical project uses at least two coordinate systems. One is a local coordinate system oriented by data collection methods and used for processing of such data. The second is usually a UTM projection and most final maps are produced in this projection. The relationship between the two is a simple shift and rotate operation since the areas we are working with are quite small.
I can see how to transform one mapset while importing into another mapset, but after that is done you obviously have a potential map version conflict when one but not the other is updated with new data.
Is there a way to overlay different projections and/or non-earth coordinate systems in grass on-the-fly? (Similar to how MapInfo and other systems handle it.)
Any comments folks?
Thanks,
John Harrop
John Harrop wrote:
Is there a way to overlay different projections and/or non-earth
coordinate systems in grass on-the-fly? (Similar to how MapInfo and
other systems handle it.)
No; re-projection has to be done explicitly.
--
Glynn Clements <glynn.clements@virgin.net>
John,
With being a geochemist I often have to work with samples taken along lines (north & non-north) and plot them on a UTM map. I personally just load all my data into a database (I like PostgreSQL, but anything is good) which has grid and utm coordinate columns. Then I have a few functions (in postgresql and MS Access) that based upon the usergrid base-point and degrees of rotation from north, transform all my coordinates to UTM or geographic. For me it's always more convient to let my database handle all the coordinate transformations because often there is a mixture of samples collected with UTM, usergrid, or geographic coordinates or even drill/trench samples (that have a collar point, orientation, and from-to distances). Now with all the samples having the same type of coordinates everything can be pulled into the map as one big layer if necessary. And regenerations are faster.
Your e-mail indicates that you are dealing with geophysics and I will guess that you are trying to overlay some of those lovely non-north grids based upon lines that the project geo layed out for you. I know they are necessary but they drive me crazy too. But again I have been hearing that PostGIST with possibly or can now handle grid data. In the future I think rdms based data will be the proper route even for cross-sections such as IP lines. For one of my clients I have PostgreSQL views that transform the sample coordinates (UTM E/N/Elev) to user-defined cross-sections coordinates to plot them up in ArcView or MapInfo.
good luck,
Phillip J. Allen
Consulting Geochemist/Geologist
Lima Peru
e-mail: paallen@attglobal.net
John Harrop wrote:
Hi,
I've not been able to come up with a comfortable way of handling projects with multiple coordinate systems in grass. Perhaps I'm missing something...
Our typical project uses at least two coordinate systems. One is a local coordinate system oriented by data collection methods and used for processing of such data. The second is usually a UTM projection and most final maps are produced in this projection. The relationship between the two is a simple shift and rotate operation since the areas we are working with are quite small.
I can see how to transform one mapset while importing into another mapset, but after that is done you obviously have a potential map version conflict when one but not the other is updated with new data.
Is there a way to overlay different projections and/or non-earth coordinate systems in grass on-the-fly? (Similar to how MapInfo and other systems handle it.)
Any comments folks?
Thanks,
John Harrop