How to get data from a GIS server in R?

Question

I have been using ArcMap to access GIS data on a spatial data server. I want to figure out how to do the same within R.

I know how to read shapefiles into R. I have successfully used maptools and rgdal to open and map locally stored shapefiles (e.g. http://www.nceas.ucsb.edu/scicomp/usecases/ReadWriteESRIShapeFiles)

My problem is when the data is not stored locally, but rather it is on an Application Server. I believe it's an Oracle database. I've been given information about the 1. Server 2. Instance (a number) 3. Database 4. User and 5. Password. Normally, I would include an example, but it's doubtful that an external user could access the servers.

For example here's how to read and plot local files in R

    library(rgdal)
    ogrInfo(".", "nw-rivers")
    centroids.rg <- readOGR(".", "nw-centroids") 
    plot(centroids.rg)

The "." points to the local directory. How would I change this to access data on a server? The actual syntax of code would be helpful.

Answer 1

You can read data from Oracle Spatial DBs using GDAL/OGR:

http://www.gdal.org/ogr/drv_oci.html

if you have the driver in your GDAL/OGR installation. If:

require(rgdal)
ogrDrivers()

shows the Oracle driver then you can use readOGR with all the parameters in the right place.

At a guess, and by analogy with the PostGIS example, I'd say try:

dsn="OCI:userid/password@database_instance:")
ogrListLayers(dsn)
s = readOGR(dsn, layername)

but I don't have an Oracle server to test it on (if I did I'd ditch it tomorrow for PostGIS, and spend the license saving on a yacht) and you don't sound certain its an Oracle server anyway. The general principle for connecting to any spatial database is the same - check you have an OGR driver, figure out what the dsn parameter looks like, try it.

Another way is to go via ODBC, or another non-spatial R database connection. However you'll likely get back the spatial data in WKB or WKT form and have to convert to SpatialWhatevers (point, lines, polygons?).

PostGIS example is here:

https://gis.stackexchange.com/questions/64950/which-is-the-best-way-of-working-with-postgis-data-in-r