[GIS] How to read Geotiff tags and pixel per pixel values using GDAL C#

cgdalgeotiff-tiffsrtm

I'm new here and I'm new at programing with GDAL C#.

My question is how I can get the value of SRTM GEOTIFF pixel to compare with it's neighbors, and how can I get the values of Geotiff tags.

Best Answer

You have two questions:

Reading pixel data from the Geotiff: Here you find a C# GDAL Read Raster Code Sample. The final reading method is called Band.ReadRaster!
Reading Geotiff-Tags: Depends which Tags you mean...
- If you want to read the GeoTransform-Parameters (Georeference-Info), you would do that with the method Dataset.GetGeoTransform.
- If you want to read the Projection-Parameters, you would do that with Dataset.GetProjectionRef.
- If you want to read any other Geotiff Tags, forget GDAL and use any other lib, like LibTiff.Net.

Related Solutions

[GIS] How to read GeoTIFF using PHP

Download the source code from here

http://www.osola.org.uk/elevations/index.htm

SRTMGeoTIFFReader.php is the clever file the reads the GeoTiff and converts the elevation values (in meters) into Lat/Lng coordinates.

I doubt this is exactly what you want but it does give you a solid base on understanding the process required to accomplish the task from your question.

(There is too much code to post here)

Python GDAL – Extracting Coordinates and Pixel Values from GeoTiff

This should get you going. The raster values are read using rasterio, and pixel centre coordinates are converted to Eastings/Northings using affine, which are then converted to Latitude/Longitude using pyproj. Most arrays have the same shape as the input raster.

import rasterio
import numpy as np
from affine import Affine
from pyproj import Proj, transform

fname = '/path/to/your/raster.tif'

# Read raster
with rasterio.open(fname) as r:
    T0 = r.transform  # upper-left pixel corner affine transform
    p1 = Proj(r.crs)
    A = r.read()  # pixel values

# All rows and columns
cols, rows = np.meshgrid(np.arange(A.shape[2]), np.arange(A.shape[1]))

# Get affine transform for pixel centres
T1 = T0 * Affine.translation(0.5, 0.5)
# Function to convert pixel row/column index (from 0) to easting/northing at centre
rc2en = lambda r, c: (c, r) * T1

# All eastings and northings (there is probably a faster way to do this)
eastings, northings = np.vectorize(rc2en, otypes=[float, float])(rows, cols)

# Project all longitudes, latitudes
p2 = Proj(proj='latlong',datum='WGS84')
longs, lats = transform(p1, p2, eastings, northings)

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Related Solutions

[GIS] How to read GeoTIFF using PHP

Python GDAL – Extracting Coordinates and Pixel Values from GeoTiff

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