geotiff-extents

compute the corner and center bounding coordinates for a geotiff

example

var fs = require('fs')
var geotiff = require('geotiff')
var epsg = require('epsg-to-proj')
var extents = require('geotiff-extents')

var data = fs.readFileSync(process.argv[2])
var im = geotiff.parse(data).getImage()
var fd = im.getFileDirectory()
var gk = im.getGeoKeys()

console.log(extents({
  tiePoint: fd.ModelTiepoint,
  pixelScale: fd.ModelPixelScale,
  width: fd.ImageWidth,
  height: fd.ImageLength,
  proj: require('proj4'),
  from: epsg[gk.ProjectedCSTypeGeoKey || gk.GeographicTypeGeoKey],
  to: epsg[4326]
}))

output:

$ node extents.js LC80700192015294LGN00_B2.TIF
{ upperLeft: [ -155.62757614534797, 59.781490186078884 ],
  lowerLeft: [ -155.46612438446172, 57.56866631571051 ],
  upperRight: [ -151.27624278582903, 59.79644709112181 ],
  lowerRight: [ -151.3822362875974, 57.58238285553903 ],
  center: [ -153.4380373185701, 58.69959098078464 ] }

and this output matches up with the listgeo command:

$ listgeo -d LC80700192015294LGN00_B2.TIF | tail -n5
Upper Left    (  352500.000, 6630000.000)  (-155.6275761,59.7814902)
Lower Left    (  352500.000, 6383370.000)  (-155.4661244,57.5686663)
Upper Right   (  596730.000, 6630000.000)  (-151.2762428,59.7964471)
Lower Right   (  596730.000, 6383370.000)  (-151.3822363,57.5823829)
Center        (  474615.000, 6506685.000)  (-153.4380373,58.6995910)

api

var extents = require('geotiff-extents')

var ex = extents(opts)

Compute the bounding and center coordinates ex given:

• opts.tiePoint - an array (or Float64Array etc) of K*6 tie point coordinates mapping (I,J,K) points in raster space to (X,Y,Z) points in model space.
• opts.pixelScale - an array (or Float64Array etc) of 3 sizes for raster spacing in model space units
• opts.width - width of the image in raster (pixel) coordinates
• opts.height - height of the image in raster (pixel) coordinates
• opts.proj - proj4(src,dst) coordinate transform implementation
• opts.from - proj string describing the tie point coordinate system
• opts.to - proj string describing the output coordinate system

The georeferencing tags are defined in more detail in 2.6.1 GeoTIFF Tags for Coordinate Transformations.

The output object ex has these properties, which map to 2-element coordinate pair arrays in the coordinate system specified by opts.to:

• ex.upperLeft
• ex.lowerLeft
• ex.upperRight
• ex.lowerRight
• ex.center

install

npm install geotiff-extents

license

BSD