Hi everyone,

 

I would like to know a good way in which to convert a
SpatialPointsDataFrame to a SpatialGridDataFrame.

The reason that I ask is that when I change the CRS of a
SpatialGridDataFrame, I inadvertently create a point data frame with the
new CRS.

 

To better illustrate my problem:

 

I have a grid file 

 

grid90m <- readGDAL("edgeroi_dem.asc")

names(grid90m) <- "edgeroi_dem" 

 

I give it a CRS

 

proj4string(grid90m)<- CRS("+init=epsg:4283")

 

Then I change it to a projected CRS

 

grid90.UTM <- spTransform(grid90m, CRS("+init=epsg:32755"))

 

Get a summary

summary(grid.UTM)

Object of class SpatialPointsDataFrame

Coordinates:

      min       max

x  738742  790718.3

y 6643860 6679923.8

Is projected: TRUE 

proj4string :

[+init=epsg:32755 +proj=utm +zone=55 +south +ellps=WGS84 +datum=WGS84
+units=m +no_defs +towgs84=0,0,0]

Number of points: 220805

Data attributes:

   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 

180.2   200.7   225.0   254.1   280.6   988.6

 

I have tried various ways to convert this points file to grid via a few
methods with resultant failure. Essentially I need to input some measure
of the pixel size.

My original thoughts were that the problem was to do with the
asymmetrical shape of my DEM layer. This may be true, but it would be
useful if people could provide some ideas on how to get around this. 

 

Cheers,

 

Brendan Malone

PhD candidate

University of Sydney 

 

 


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