topic Re: Shapefile Projection in Developers Questions

Shapefile Projection

ABDALLAMOHAMED — Mon, 13 Mar 2017 23:23:36 GMT

Hello.

I have 100 US. metro cities in shapefiles and would like to project them. I would like to know the most suitable projection type for them. Currently they are in Geographic Coordinate System: GCS_North_American_1983
Datum: D_North_American_1983.

Thanks a a lot

Re: Shapefile Projection

DanPatterson_Retired — Mon, 13 Mar 2017 23:59:23 GMT

Currently on PRO, but it is the same for ArcMap.

What is the best, depends on your spatial area coverage. You can begin your journey in many ways, but I find the interface from ArcToolbox the easiest to remember

do some reading, start with what is used in your area, or by the federal gov't etc. There are lots of choices lambert's and Albers variants tend to be recommended depending whether your E/W extent is wider than your N/S.

Others will weigh in with opinions, the above guides you to the 'where are'

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 00:15:16 GMT

Dan,

Let me check them, and let you know which one works

Thanks a lot

Re: Shapefile Projection

DanPatterson_Retired — Tue, 14 Mar 2017 00:20:01 GMT

remember, that the continental scale ones are best for a well spread out set of data... if all your points are on one coast or the other, then you might begin to examine those at a more regional level or even State-based. Good luck... but do check what is used by the various levels of government. Here in Canada, they are pretty specific as to what they use on a country and province wide basis

Re: Shapefile Projection

RebeccaStrauch__GISP — Tue, 14 Mar 2017 00:35:57 GMT

Also keep in mind, that depending on what you are needing to do with the points (polys?), if if the shapefile has a proper .prj (projection) file and/or if you bring it into a file gdb with the correct projection/cooredinate-system assigned, the data should project-on-the-fly. In otherwords, you don't necessarily need to project them.

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 00:48:56 GMT

They are in polygons, and I selected two metro cities from each state. So they represent the 50 US states. Currently I'm reading an article talking about UTM is the best one.

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 00:50:54 GMT

The shapefile has no proper .prj file. I wanted to project them so that I can run global Moran's I and LISA and GWR

Re: Shapefile Projection

RebeccaStrauch__GISP — Tue, 14 Mar 2017 00:50:57 GMT

UTM would NOT be a good choice is you are showing across the 50 states.

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 00:54:37 GMT

Some of metro cities are across states like chicago, kansas and St Louis. I want to project each city separately

Re: Shapefile Projection

RebeccaStrauch__GISP — Tue, 14 Mar 2017 00:58:16 GMT

I want to project each city separately

then it might be ok. you would just have to figure out the best UTM zone for each. Like any projection, you will get distortion in one form or another.

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 01:03:07 GMT

Can you give more explanation on UTM, I never use it before and don't how to

Re: Shapefile Projection

RebeccaStrauch__GISP — Tue, 14 Mar 2017 01:10:19 GMT

I think the help would explain better than I ever could

What are projected coordinate systems?—Help | ArcGIS Desktop

But in short, there are 60 UTM zones, each representing 6° (i.e. 60 x 6 = 360°). so it is typically used for projects with smaller footprints.

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 01:16:12 GMT

Okay let me read it and see

Thanks a lot

Re: Shapefile Projection

DanPatterson_Retired — Tue, 14 Mar 2017 01:50:18 GMT

unless you want to produce separate files for your separate city clusters... pick one like albers for instance, and just create bookmarks to zoom into those locations. Then you have the over-arching perspective view and a more regionalized view... UTM is not the way to go. I would give a real think about what it is you want to do. It doesn't sound like you have any mission-critical geometry calculations to do... just some mapping to show whatever it is you want to show.

Keep it simple and leave the reading for the weekend, pick a country wide perspective and start from there, otherwise you will end up in a hopeless state of unnecessary work and potential confusion

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 02:12:16 GMT

I just want to calculate global moran's I, LISA, and QWR

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 02:15:52 GMT

I forgot to add i'm going to produce separate file for each metro city, because i can't run global moran's I on the overall 100 metro cities together, i have to do them separately

Re: Shapefile Projection

DanPatterson_Retired — Tue, 14 Mar 2017 02:21:47 GMT

So you should read the help topic first for Global Morans, for instance, because the need to project the data is moot if your geographic coordinate system is within 30 degrees since the calculations will use a chordal distance. Again, check it out before you start doing a whole load of unnecessary work like projecting 50+ pairs of data into different coordinate systems.

Re: Shapefile Projection

ABDALLAMOHAMED — Tue, 14 Mar 2017 02:26:40 GMT

Okay, i will do that

Thanks a lot for your help. Appreciated.