topic Re: Generating Vector Index Grids: in Geoprocessing Questions

Generating Vector Index Grids:

MarkEnglish — Tue, 26 Apr 2011 20:23:21 GMT

Hello: I am beggining a project that requires an index grid. I basically would like to generate three grids (polygon) that cover my project area at 1 mille, 10 miles, and 100 miles. I don't need it to follow any pre-existing boundaries, although its required to cover my project area. Oh, and I"m still using 9.3.1? Thanks in advance.
Mark

Re: Generating Vector Index Grids:

DanPatterson_Retired — Tue, 26 Apr 2011 21:16:47 GMT

called "fishnet"
http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?id=1782&pid=1777&topicname=Create_Fishnet_(Data_Management)
go figure...

Re: Generating Vector Index Grids:

MarkEnglish — Thu, 28 Apr 2011 09:53:19 GMT

Hi Dan. I saw FIshnet was available before I posted, but was unsure of its capabilites. So, I tried generating a 1 mile grid, but was unsuccessful. Have you happened to use FishNet before? If so, any idea on creating the grid using miles? It doesn't appear to have the option for units. Thanks Dan...

Re: Generating Vector Index Grids:

DanPatterson_Retired — Thu, 28 Apr 2011 12:06:38 GMT

a fishnet only makes sense if you are using/creating projected data (eg. UTM, state plane etc etc). If your coordinates are in meters, simply "do the math" to get the results in feet. If your data are in decimal degrees for your dataframe, use a projected coordinate system for it and make sure that the outputs are projected.

Re: Generating Vector Index Grids:

MarkEnglish — Mon, 02 May 2011 00:09:31 GMT

Thanks Dan. Before I recieved your most recent post, I projected my data in UTM, and 'did the math' within FishNet to accomodate a mile. I quality assured the distance results, and was pleased with their outcome. The only concern was the grid came out with uniform cells from east to west and north to south. They didn't follow the curviture of the projected data, instead were straight. The grid data was also kicked out in UTM, so I'm not sure why this occured. I'll continue to tinker with the projection. Any thoughts?

Re: Generating Vector Index Grids:

DanPatterson_Retired — Mon, 02 May 2011 00:51:16 GMT

Long/lat has curvature, UTM doesn't, so a fishnet (aka polygon grid) will be oriented east/west and north/south in metric (feet for you) units. If your need to orient a grid to long/lat that is a mile wide then you are going to have to do more math, but the gain would be small

Re: Generating Vector Index Grids:

RobertAnderson2 — Thu, 18 Aug 2011 21:43:11 GMT

Hello,
I am attempting to create a map book through data driven pages. The area contains an un-even patchwork of housing and hotels. An index grid is not useful because the grids cut through some buildings and houses. I need to create polygons around each individual area and size them to fit on each page in the map book. I am new to ArcMap 10 and I am learning, but I also need some guidance. I do not know very much about Python. I have read about fishnet. Does anyone have any information I might use?
Thank You...

Re: Generating Vector Index Grids:

DaleHoneycutt — Thu, 18 Aug 2011 22:36:33 GMT

The Fishnet tool is a hard one to figure out. The topic How Create Fishnet Works can help you figure out the parameters and what values you should use.

Grid Index Features is a tool in the cartography toolbox that creates regular grids as well. I haven't used it. See Creating Grid Index Features for more info.

You should be able to create your custom grid index by creating a new polygon feature class and digitizing new polygons. Here's a quote from the topic What are data driven pages? that confirms you can use your own index (it doesn't have to be a grid):

The index layer does not have to be a grid. It can be map features. For example, you can create Data Driven Pages using a polygon layer of U.S. states. In this case, a page is created for each state.