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Subject Author Date
Warping methods, confused Sam G. 11-30-2004
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Posted by Sam G. on November 30, 2004, 12:43 pm
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 I'm relatively new to gis and am trying to model a small area.
However, the data is in geographic projection using WGS84. I'd like to
convert it to UTM with WGS84. Can someone explain the different
methods for doing this. How does delauney triangulation, polynomial
and other methods differ. I'm very confused at the moment.


Posted by CadGuy on November 30, 2004, 6:03 pm
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 Hi,

I do not understand the mathermatics behind the warping function of
most imagery programs and I think very few people do although they
will never admit it.
As to your problem, there are many free software that will convert
between the different datums/projections that you require. Try any of
the following:
1. Microdem
2. Tatuk GIS Calculator
3. Microstation Geocoordinator (not free but they have a trial
version)

hth


Posted by Prof. Cliff Mugnier on November 30, 2004, 8:07 pm
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skyman302@gmail.com (Sam G.) wrote in message
> I'm relatively new to gis and am trying to model a small area.
> However, the data is in geographic projection using WGS84. I'd like to
> convert it to UTM with WGS84. Can someone explain the different
> methods for doing this. How does delauney triangulation, polynomial
> and other methods differ. I'm very confused at the moment.


Geographic is NOT a projection. It is the basic coordinate system of
geographic data (Latitude & Longitude). WGS84 is a particular datum
or system of Latitude and Longitude. UTM is a grid system with
specific rules for a Transverse Mercator projection.

Delauney triangulation, polynomial and other methods of "warping" do
NOT apply to getting geographic coordinates (in some datum) into UTM
coordinates.

Explain what GIS package you are working in and people will be better
able to help you along if you don't want to read the manual.

C. Mugnier
LSU


Posted by Sam G. on December 1, 2004, 9:25 am
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cjmce@LSU.edu (Prof. Cliff Mugnier) wrote in message
> skyman302@gmail.com (Sam G.) wrote in message
> > I'm relatively new to gis and am trying to model a small area.
> > However, the data is in geographic projection using WGS84. I'd like to
> > convert it to UTM with WGS84. Can someone explain the different
> > methods for doing this. How does delauney triangulation, polynomial
> > and other methods differ. I'm very confused at the moment.
>
>
> Geographic is NOT a projection. It is the basic coordinate system of
> geographic data (Latitude & Longitude). WGS84 is a particular datum
> or system of Latitude and Longitude. UTM is a grid system with
> specific rules for a Transverse Mercator projection.
>
> Delauney triangulation, polynomial and other methods of "warping" do
> NOT apply to getting geographic coordinates (in some datum) into UTM
> coordinates.
>
> Explain what GIS package you are working in and people will be better
> able to help you along if you don't want to read the manual.
>
> C. Mugnier
> LSU

I'm looking into different programs to convert coordinates at the
moment so I'm trying to evaluate features. I forgot to mention that
I'm working with gridded ned data if that clears up anything. Thus, I
need to convert raster images, not just individual points.


Posted by Global Mapper Support on December 1, 2004, 7:27 pm
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> cjmce@LSU.edu (Prof. Cliff Mugnier) wrote in message
>> skyman302@gmail.com (Sam G.) wrote in message
>> > I'm relatively new to gis and am trying to model a small area.
>> > However, the data is in geographic projection using WGS84. I'd like to
>> > convert it to UTM with WGS84. Can someone explain the different
>> > methods for doing this. How does delauney triangulation, polynomial
>> > and other methods differ. I'm very confused at the moment.
>>
>>
>> Geographic is NOT a projection. It is the basic coordinate system of
>> geographic data (Latitude & Longitude). WGS84 is a particular datum
>> or system of Latitude and Longitude. UTM is a grid system with
>> specific rules for a Transverse Mercator projection.
>>
>> Delauney triangulation, polynomial and other methods of "warping" do
>> NOT apply to getting geographic coordinates (in some datum) into UTM
>> coordinates.
>>
>> Explain what GIS package you are working in and people will be better
>> able to help you along if you don't want to read the manual.
>>
>> C. Mugnier
>> LSU
>
> I'm looking into different programs to convert coordinates at the
> moment so I'm trying to evaluate features. I forgot to mention that
> I'm working with gridded ned data if that clears up anything. Thus, I
> need to convert raster images, not just individual points.

You can use Global Mapper (http://www.globalmapper.com) to load NED files
(and lots of other formats) and reproject them before saving out to a new
file. To do so, just load the NED file, change the view/export projection on
the Projection tab of the configuration dialog to UTM (or whatever other
projection you need), then use the appropriate File->Export Raster and
Elevation data menu command to save out the new file.

If you have lots of files to convert, there is also a batch
conversion/reprojection option on the File menu.

Let me know if I can be of further assistance.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com




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