topic Re: UTM for Texas in Coordinate Reference Systems Questions

UTM for Texas

LanoYado — Thu, 13 Oct 2016 14:00:59 GMT

Because I am not GIS expert, so may be my question a quite basic question in GIS. I am working on Texas area (The whole state) but when I want to use TIN it says it's recommended to use projected coordinate. When I come to find the block or unit of the area using UTM, I found there are three blocks cover the whole state (13, 14, and 15). My question is, which one should I choose to cover the whole state?

Thanks in advance

Re: UTM for Texas

MicahBabinski — Thu, 13 Oct 2016 14:23:05 GMT

Hi Lano,

That depends on what you will do with the data. The choice you make should be based in what characteristics you want to preserve and which you are ok with distorting between shape, area, distance, and direction. Texas is a big state - three UTM Zones and five state plane zones. You might want to see if the state of Texas provides any data to the public in a projected coordinate system and go with that.

Good luck.

Re: UTM for Texas

LanoYado — Thu, 13 Oct 2016 14:30:58 GMT

Thanks Micah. I will google if the state provides any data in UTM.

Re: UTM for Texas

ChrisDonohue__GISP — Thu, 13 Oct 2016 15:59:34 GMT

To build on what Micah Babinski stated, since Texas has multiple UTM zones, picking one UTM standard zone to try to use for the whole state won't work that well. Instead, you want a projected coordinate system that covers the whole state.

That said, there are likely several available and it will not be obvious at first which one to choose. Essentially all coordinate systems are a trade off between 4 factors: shape, area, distance, and direction. There is no coordinate system that preserves all 4; instead, each coordinate system is set up to preserve some of the factors at the expense of others. So you will want to choose a coordinate system that matches the goals of your project.

For example, if the goal is to have polygons with the correct area but are not so worried about their shape getting distorted somewhat, an Equal-Area coordinate system would be a good choice. However, Equal-Area would not be a good choice if the goal is to show the true distance of lines.

Choosing the Right Map Projection - Learning - Source: An OpenNews project

Chris Donohue, GISP

Re: UTM for Texas

LanoYado — Thu, 13 Oct 2016 16:38:24 GMT

Thanks Chris, clear reason and good information.

Re: UTM for Texas

ChrisDonohue__GISP — Thu, 13 Oct 2016 17:11:09 GMT

I should also add that for many GIS people (myself included) the subject of projections and coordinate systems is not something that comes easily at first. So if it seems mystifying, read up on it and then ask questions here on GeoNet. There are many knowledgeable people here who can help. And for the total puzzlers, here on GeoNet we are often blessed with the expertise of MKennedy-esristaff (ESRI coordinate systems expert).

Chris Donohue, GISP

Re: UTM for Texas

LanoYado — Thu, 13 Oct 2016 17:32:29 GMT

Thanks Chris, many times, when I ask question here in GeoNet, it shortens the time to me and gives me a right course to read about. I greatly appreciate the helps I got form all here in GeoNet.

Re: UTM for Texas

DanPatterson_Retired — Thu, 13 Oct 2016 20:49:18 GMT

I am sure Melita Kennedy‌ would endorse people becoming familiar with a well know repository of coordinate systems and projections. One can't go wrong with one with the name Texas in it

NAD83 / Texas State Mapping System: EPSG Projection -- Spatial Reference

or a lambert conformal conic with a Texas flavor

NAD83 / Texas Centric Lambert Conformal: EPSG Projection -- Spatial Reference

But I am sure there are others there as well... like these

Spatial Reference List -- Spatial Reference

From the help topics

What are map projections?—Help | ArcGIS for Desktop

and from that link

http://desktop.arcgis.com/en/arcmap/latest/map/projections/pdf/projected_coordinate_systems.pdf