Functions to make it easy to add GPS traces to rstats Rayshader scenes, process DEM data and to overlay ggmap imagery
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README.md

Geoviz

Helper functions to draw rayshader scenes.

  • From UK OS Terrain 50, NASA ASTER and EU Copernicus DEM (Digital Elevation Model) data
  • With elevation shading (green valleys and snow capped peaks, or anything else you want)
  • With map and satellite overlays from ggmap
  • with added GPS tracks

Rayshader is an awesome bit of kit! I'm just doing some colouring in.

Installing

devtools::install_github("neilcharles/geoviz")

Geoviz helps you to draw images like these.

rendered scene

rendered scene

A note about Google Maps

The example below uses a Stamen map overlay because Google Maps now requires an API key. See ggmap.

If you want to do anything Googley with ggmap you'll need to register for an APIkey and before calling geocode() from ggmap or ggmap_image() from geoviz, run the following lines.

library(ggmap)

register_google(key = your_google_key)

Google will want billing details but you get plenty of free requests per month before charging begins and you can apply a spend cap of zero if you want to.

A quick example... see lower down the page for how to do this with your own data

library(geoviz)
library(rayshader)

#Load an example IGC (GPS track log) file

igc <- example_igc

#Load a small example elevation raster showing a piece of the English Lake district

DEM <- example_raster

#Set a few parameters to be used by rayshader (see rayshader's documentation for options etc.)

exaggerate <- 1

increase_resolution <- 1   #useful when you're cropping sections out of your DEM

sunangle = 270

zscale = 25

#Get a Stamen map using ggmap that will cover our DEM

ggmap_overlay <- ggmap_image(DEM, source = "stamen", maptype = "watercolor", zoom = 10)

ggmap_overlay[,,4] <- 0.3  #sets the transparency of this overlay

#Make an elevation shading layer with dark valleys and light peaks (not essential but I like it!)

elevation_overlay <- elevation_shade(DEM, elevation_palette = c("#000000", "#FFFFFF"))

elevation_overlay[,,4] <- 0.6  #sets the transparency of this overlay



#Calculate the rayshader scene (see rayshader's documentation)

elmat = matrix(
  raster::extract(DEM, raster::extent(DEM), method = 'bilinear'),
  nrow = ncol(DEM),
  ncol = nrow(DEM)
)

scene <- elmat %>%
  sphere_shade(sunangle = sunangle, texture = "bw") %>% 
  add_overlay(elevation_overlay) %>%
  # add_water(rayshader::detect_water(elmat), color="imhof4") %>%
  add_overlay(ggmap_overlay)


#Render the rayshader scene

rayshader::plot_3d(
  scene,
  elmat,
  zscale = zscale / increase_resolution / exaggerate,
  solid = FALSE,
  shadow = TRUE,
  shadowdepth = -100
)

rendered scene

#Add the gps track

add_gps_to_rayshader(
  DEM,
  igc$lat,
  igc$long,
  igc$altitude,
  line_width = 1.5,
  lightsaber = TRUE,
  colour = "red",
  zscale / increase_resolution / exaggerate,
  ground_shadow = TRUE
)

rendered scene

DEM Data Sources - EU Copernicus

EU coverage.

Copernicus map tiles are large, typically 3-5GB each and covering a country sized area. Download them here

big_DEM <- raster::raster("path/to/file/eu_dem_v11_E30N30.TIF")

zscale <- 25

DEM Data Sources - OS Terrain 50

UK coverage. Copernicus also covers the UK if you want to use that instead.

To draw scenes of UK geography using OS Terrain 50 data.

Download OS Terrain 50 and unpack it so that you have a "data" directory.

Use the following line to stitch all of the GRID files together into a single raster of the entire UK, or if you don't want to wait that long or have a lower powered machine that can't handle the whole UK mosaic, move a subset of GRID zip files out of the data directory and point the function at that subset instead.

mosaic_uk_grid("path/to/grid/data/")  #ONLY RUN THIS ONCE TO CREATE THE WHOLE UK MOSAIC RASTER. IT MIGHT TAKE A WHILE.

If you find you run out of memory, try these lines before you call mosaic_uk_grid().

library(raster)
rasterOptions(todisk=TRUE)

Load the merged raster file

big_DEM <- raster::raster("mosaic_uk_grid.grd")

zscale <- 50

DEM Data Sources - NASA ASTER

Whole world coverage but quite noisy. Copernicus is better if you're mapping in the EU.

Download DEM files from here. Search for "ASTER" in the top left box and select "ASTER Global Digital Elevation Model V002" underneath the map. You won't realistically be able to stitch together a single file of the whole world - it would be enormous - so just download the areas you need.

Stitching together the separate files is the same proces as for OS Terrain 50.

mosaic_ASTER("path/to/data/")

If you find you run out of memory, try these lines before you call mosaic_ASTER().

library(raster)
rasterOptions(todisk=TRUE)

Load the merged raster file

big_DEM <- raster::raster("mosaic_ASTER.grd")

zscale <- 30

Slicing pieces out of the DEM

You probably don't want to render everything in your DEM data, you'll want to cut out a piece. Geoviz has two functions to help you do this.

Crop out a square around a point...

library(ggmap)

register_google(key = your_google_key)

#Note that the below will only work if you point it at DEM data that contains Keswick! 

coords <- geocode("Keswick, UK")

DEM <- crop_raster_square(big_DEM, coords$lat, coords$lon, square_km)

Or crop a section from your DEM to fit a GPS track...

DEM <- crop_raster_track(big_DEM, igc$lat, igc$long, width_buffer = 2)

Loading GPS tracks

You can load GPS track data any way that you like and pass decimal lat-longs as vectors to geoviz functions (see code examples above).

If your GPS data is in IGC format - commonly used for glider flight data - then geoviz has a function read_igc(), which will do all the formatting work for you.

igc <- read_igc("path/to/your/file.igc")

Adding GPS traces to Rayshader scenes

Geoviz converts decimal lat-long GPS traces into rayshader's coordinate system and then plots the GPS track using the funtion add_gps_to_rayshader(). Rather than adding a trace to a scene, if you just want to convert lat-long points into rayshader's coordinates and see the converted data (e.g. so you can add your own arbirary rgl shape to the scene or for use with rayshder's render_label() function), use latlong_to_rayshader_coords().