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I have a list of addresses that I have geocoded to get the corresponding longitude and latitude.

> AddressDetail <- geocode(match_address)
> coordinates(AddressDetail) <- c("lon", "lat")

Now I believe I should assign a projection so that R knows how the lon/lat coords are set up

> proj4string(AddressDetail) <- CRS("+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs")

Now I read in the shapefile that uses the NZMG projection

> Shape_MB = readOGR("/Work in progress/MB06_LV2/", "MB06_LV2")

Now this is where it starts to go wrong. I try transforming the projection of the lon/lat addresses into NZMG projection.

> AddressDetail <- spTransform(AddressDetail_v2, CRS("+proj=tmerc +lat_0=0 +lon_0=173 +k=0.9996 +x_0=1600000 +y_0=10000000 +ellps=GRS80 +units=m +no_defs")                                                      
non finite transformation detected:
lon lat  
Error in spTransform(xSP, CRSobj, ...) : failure in points 
In addition: Warning message:
In spTransform(xSP, CRSobj, ...) : 9 projected point(s) not finite

So when I continue on to use the over function to find the corresponding census meshblock index of the polygon that the address is within I get the following error. 

> temp <- over(AddressDetail_v2,Shape_MB,MB06)
Error: identicalCRS(x, y) is not TRUE

I'm a bit of a novice with geospatial stuff in R so would appreciate any advice!

nicht_mal_owl
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  • Check the coordinates in your "AddressDetail" data. I suspect that you have a few points, 9 to be exact, that are not defined correctly (e.g., missing "-"). – Jeffrey Evans Jan 13 '14 at 18:46
  • It seems that you are using NZTM instead of the NZMG definition. See the first answer to this question. (My apologies - I would normally put this as a comment, but I am not allowed to comment yet.) – cengel Sep 10 '13 at 14:44

1 Answers1

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Now that I have significantly more R experience under my belt, it's time to answer this question...

First was to make sure the geocoded address was converted to a spatialpoint cleaner:

AddressDetail <- geocode(match_address)
coordinates(AddressDetail) <- ~lon + lat

Then the relevant projection was assigned to the spatialpoint

wgs84 <- '+proj=longlat +datum=WGS84'
projection(AddressDetail) <- wgs84

From here I wanted to project the geocoded point to the same projection of the meshblocks I want to match the points over.

So read in the meshblock shapefile:

Shape_MB <- readOGR("/Work in progress/MB06_LV2/", layer = "MB06_LV2")

Then simply copy the projection of the meshblock shapefile when transforming the geocoded points:

AddressDetail <- spTransform(AddressDetail, crs(projection(Shape_MB)))

So it really doesn't matter whether the meshblock shapefile is NZMG or something else, just copy the projection and then projection everything else based on that.

Thanks, Alistair

nicht_mal_owl
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