topic Re: add .shp and .shx files to a new map in Mapping Questions

add .shp and .shx files to a new map

TiffanyJohnson — Wed, 23 Nov 2016 17:00:33 GMT

I am new to ArcGIS map and I am trying to import files in from MapInfo. I already made the conversion of several of the files to what were supposed to be usable formats (.shp, .shx, .dbf), but when I open ArcMap and attempt to add data to a new map, the files don't appear in the folder. I am not sure what I am doing wrong >.<

Re: add .shp and .shx files to a new map

JoeBorgione — Wed, 23 Nov 2016 17:14:03 GMT

A 'shapefile' is actually made up of a minimum of three different files: <name>.shp, <name>.shx and <name>.dbf.

The .shp file contains the geometry data and the .dbf holds the attribute table. The .shx is the middle man that links the two together.

While I'm not familiar with MapInfo, you might want to double check that the export process completed properly and in the the directory you want. You may need to create a connection to that directory (folder) which you can do on the fly in ArcMap or keep it persistent in AcrCatalog.

Re: add .shp and .shx files to a new map

DarrenWiens2 — Wed, 23 Nov 2016 19:47:31 GMT

Is ArcMap able to recognize any shapefiles at all?

Re: add .shp and .shx files to a new map

VinceAngelo — Wed, 23 Nov 2016 20:15:34 GMT

No, the .shx only provides direct read references into the .shp file. It's a naming convention adopted from the PRIMOS operating system (for the Prime minicomputers on which Arc/Info was originally developed) which provided a shadow fixed-width file for offsets to direct access of the variable record width files. All the *x files of ArcGIS are indexes into the similarly named variable-width files.

The dBase file has a fixed table header and N fixed field headers, that define the start and width of the fixed records. The only link between .shp and .dbf is record number.

You can usually regenerate the .shx if it is lost, since the .shp has internal offsets as well, but if the .shp or .dbf is lost, the geometry or attributes are gone.

- V

Re: add .shp and .shx files to a new map

JoeBorgione — Wed, 23 Nov 2016 20:20:39 GMT

Oops.... I was told (many many moons ago) it acts as an index between the two. My bad....

Re: add .shp and .shx files to a new map

VinceAngelo — Wed, 23 Nov 2016 20:24:37 GMT

Yeah, that bit of lore has been repeated long after the original mistaken assertion was made. It sounds good, but it isn't true. No biggie.

- V

Re: add .shp and .shx files to a new map

ChrisDonohue__GISP — Tue, 29 Nov 2016 18:04:55 GMT

Expanding on what Darren Wiens suggested, if it turns out the shapefiles cannot be recognized by your copy of ArcGIS, something to try would be to run the Check Geometry (Data Management toolbox) Geoprocessing tool

ArcGIS Help (10.2, 10.2.1, and 10.2.2) - Check Geometry

Shapefiles are a fairly open format and not all shapefiles are ESRI-complaint, so Check Geometry may point out any issues. If issues do show up, one can run Repair Geometry (Data Management) to attempt a fix on the shapefile. While not a guaranteed fix, I've found it quite often turns a bad shapefile into something usable.

ArcGIS Help (10.2, 10.2.1, and 10.2.2) - Repair Geometry

Note - be sure to back up your shapefiles before running this tool, as Repair Geometry alters the input file.

Chris Donohue, GISP