CODEWITHSUNDEEP
rspatstat
quartzl
quartzl

Reputation: 57

R spatstat - Different window unit between ppp and owin (window) object

How can we transform "unit" of window between ppp objects and owin objects?

I am trying to analyze spatial data collected from open street map.

First, I get POI data around Singapore, then transform them to ppp objects

if(!require("osmdata")) install.packages("osmdata")
library(osmdata)
q <- getbb("Singapore") %>%
opq() %>%
add_osm_feature("amenity")

places <- osmdata_sf(q)
police <- places$osm_points %>% 
   filter(amenity == "police") %>%
   st_transform(., "+proj=utm +zone=19 +ellps=GRS80 +datum=NAD83")

police.sp  <- as(police, "Spatial")  # Create Spatial* object
police.ppp <- as(police.sp, "ppp")      # Create ppp object
class(police.ppp)

Later on, I tried to insert a .shp object I found from the gov website to create a Singapore shape to input as Window() to police.ppp object. 

s    <- readOGR(".", "Region_Census2010")
sg    <- as(s, "owin")

However, upon calling summary of the two, I saw the two have really different ranges

summary(sg)
enclosing rectangle: [2637.87, 56396.44] x [15748.72, 50256.33] units
                     (53760 x 34510 units)

summary(police.ppp)
Window: rectangle = [1280705.4, 1323492.3] x [19833441, 19854045] units
                    (42790 x 20600 units)

As a result, all of the police points were out of the map when I try to plot the files.

Is there any way to adjust the units? Did I do any steps wrong there?

Please help!

Thank you!

Upvotes: 0

Views: 282

Answers (1)

Ege Rubak
Ege Rubak

Reputation: 4507

Make sure you use the same CRS for both datasets. After reading in s you should use st_transform or spTransform to convert to the same coordinate system (UTM zone 19) as the police points.

Upvotes: 2

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