Which is the correct proj4string for shapefile?
In your case the projection is “EPSG:27700”. If you have projections defined for the shapefile you can assign the projection when you create the SpatialPointsDataFrame and then use the projection definition from your imported shapefile. Using “readOGR” from the rgdal package will retain the projection definitions.
What do you need to reproject data in R?
When you reproject the data, you specify the CRS that you wish to transform your data to. This CRS contains the datum, units and other information that R needs to reproject your data. the CRS that you wish to transform that object too.
Which is the last portion of a proj4 string?
Data tip: the last portion of each proj4 string is +towgs84=0,0,0 . This is a conversion factor that is used if a datum conversion is required. You will not deal with datums in this tutorial series. Next, let’s view the extent or spatial coverage for the sjer_aoi spatial object compared to the state_boundary_us object.
Can You reproject a point layer into a CRS?
Data Tip: spTransform () will only work if your original spatial object has a CRS assigned to it AND if that CRS is the correct CRS! Next, let’s reproject your point layer into the geographic – latitude and longitude WGS84 coordinate reference system ( CRS ).
How to read a shape file in R?
Due to the sp and rgdal packages in R you can manipulate shapefiles directly in R: now lets map the world boarders. You can find a little dataset for that here: thematicmapping.org. shape=readOGR(“TM_WORLD_BORDERS_SIMPL-0.3.shp”, layer=”TM_WORLD_BORDERS_SIMPL-0.3″) #will load the shapefile to your dataset.
When to use proj4string instead of readogr?
Therefore, proj4string is expedient only if we use another import function for example readShapeSpatial (for polygons, lines or points) or by using readOGR, but in the case that the shapefile does not contain the coordinates/projection:
Do you need to define a projection in R?
To answer your specific question, yes, you should define a projection if one is not specified. Choosing the correct value for proj4string for shapefile reading in R? And if one wants to reproject a spatial object in R, i.e., change its projection, then refer to: Thanks for contributing an answer to Geographic Information Systems Stack Exchange!