Utility Scripts

General-purpose tools for metadata, histograms, and image analysis

Utility Scripts

General-purpose utilities for working with geospatial raster data, including metadata generation, statistical analysis, and size calculations.

gdal2metadata.py

Generates FGDC (Federal Geographic Data Committee) metadata XML from GDAL-supported raster files.

Usage

python gdal2metadata.py [options] in_Geo.tif in_FGDCtemplate.xml output.xml

Parameters

in_Geo.tif · string · required

Input georeferenced raster file

in_FGDCtemplate.xml · string · required

Input FGDC metadata template XML file

output.xml · string · required

Output populated FGDC metadata XML file

Options

-debug · flag

Print detailed image information during processing

-mm · flag

Compute and report min/max values

-stats · flag

Compute and report statistics

-hist · flag

Report histograms

Metadata Fields Populated

Automatically extracts and populates:

Spatial Information

• Coordinate system - Projection name and parameters
• Datum and spheroid - Target body, radii, flattening
• Resolution - Pixel size in degrees or meters
• Extent - Bounding coordinates (westbc, eastbc, northbc, southbc)
• Image dimensions - Rows and columns

Projection Parameters

Supports and extracts parameters for:

• Equirectangular
• Mercator
• Transverse Mercator
• Sinusoidal
• Robinson
• Stereographic
• Polar Stereographic
• Orthographic

Technical Details

• Data type and bit depth
• NoData values
• Scale and offset

Example

# Basic metadata generation
python gdal2metadata.py input.tif fgdc-template.xml output_metadata.xml

# With statistics and debugging
python gdal2metadata.py -debug -stats input.tif fgdc-template.xml output_metadata.xml

Template File

Requires an FGDC XML template with placeholder elements. The script populates:

<horizsys>
  <planar>
    <mapproj>
      <mapprojn>Equirectangular</mapprojn>
      <equirect>
        <stdparll>0</stdparll>
        <longcm>0</longcm>
      </equirect>
    </mapproj>
  </planar>
</horizsys>

Coordinate Normalization

Longitudes are automatically normalized to -180 to 180 range for FGDC validation compliance.

Requirements

Dependencies:

• Python 2.7+ or Python 3.x
• GDAL Python bindings
• lxml or xml.etree for XML processing

# Install lxml (recommended)
conda install -c conda-forge lxml

---

gdal_hist.py

Exports raster histogram data in tab-delimited format for analysis and visualization.

Usage

python gdal_hist.py [options] datasetname

Parameters

datasetname · string · required

Input raster dataset

Options

-mm · flag

Compute and display min/max values

-stats · flag

Compute and display statistics (min, max, mean, stddev, RMS)

-hist · flag

Export histogram data (required)

-unscale · flag

Apply scale and offset to unscale values to original units

At least one flag (-mm, -stats, or -hist) must be specified.

Output Format

Statistics Output

Min=0.00, Max=50.00, Mean=15.23, StdDev=8.45, RMS=17.42

Histogram Output

level    value      count    cumulative
0        0.00       1234     0.012340
1        0.20       2345     0.035790
2        0.40       3456     0.070350
...

Columns:

• level - Bin number
• value - Center value of bin
• count - Number of pixels in bin
• cumulative - Cumulative percentage (0-1)

Example

# Export histogram only
python gdal_hist.py -hist slope.tif > slope_histogram.txt

# Statistics and histogram
python gdal_hist.py -stats -hist dem.tif > dem_analysis.txt

# Unscaled values
python gdal_hist.py -unscale -stats -hist scaled_data.tif > unscaled_stats.txt

Scale and Offset

When -unscale is used:

value = (raw_value × scale) + offset

Reads scale and offset from raster metadata.

Multi-band Files

For multi-band files, each band is processed separately:

Band 1 Block=256x256 Type=Float32, ColorInterp=Gray
Min=0.00, Max=50.00, Mean=15.23, StdDev=8.45, RMS=17.42
level    value      count    cumulative
...

---

slope_histogram_cumulative_graph.py

Creates histogram and cumulative distribution visualizations from tabular histogram data.

Usage

python slope_histogram_cumulative_graph.py [options] input.tab output.png

Parameters

input.tab · string · required

Input tab-delimited histogram file (from gdal_hist.py)

output.png · string · required

Output PNG image file

Options

-name · string

Title for the plot

-name "Mars Landing Site A"

Input File Format

Expects tab-delimited format from gdal_hist.py:

level    value    count    cumulative
0        0.00     1234     0.012340
1        0.20     2345     0.035790

Output Visualization

Generates a dual-axis plot:

• Left Y-axis - Frequency histogram (gray filled area)
• Right Y-axis - Cumulative distribution (blue line)
• X-axis - Value (typically slope in degrees)
• Vertical line - Reference line at x=15 (suitable for slopes)

Example

# Generate histogram from DEM slope
python gdal_hist.py -hist slope.tif > slope_hist.txt

# Create visualization
python slope_histogram_cumulative_graph.py -name "Site Alpha" \
  slope_hist.txt slope_histogram.png

Customization

The script can be modified to:

• Change reference line position (default: x=15)
• Adjust color scheme
• Modify axis labels
• Change figure size

Requirements

Dependencies:

• Python 3.x
• pandas
• matplotlib

conda install -c conda-forge pandas matplotlib

---

gdalSize.py

Calculates uncompressed raster file size based on geographic extent and resolution.

Usage

python gdalSize.py minlong minlat maxlong maxlat resolution bitType bands infile

Parameters

minlong · float · required

Minimum longitude (degrees)

minlat · float · required

Minimum latitude (degrees)

maxlong · float · required

Maximum longitude (degrees)

maxlat · float · required

Maximum latitude (degrees)

resolution · float · required

Resolution in meters per pixel

bitType · integer · required

Bit depth: 8, 16, or 32

bands · integer · required

Number of bands

infile · string · required

Reference image for projection information

Output

Reports estimated file size:

1234.5 in Megabytes
1.2 in Gigabytes

How It Works

1. Reads projection from reference image
2. Transforms geographic bounds to projected coordinates
3. Calculates dimensions based on resolution
4. Computes uncompressed size: lines × samples × bands × bytes_per_pixel

Size Calculation

Bit Depth	Bytes per Pixel
8	1
16	2
32	4

Size = (extent_x / resolution) × (extent_y / resolution) × bands × bytes_per_pixel

Example

# Calculate size for Mars region
# Bounds: -180 to 180 lon, -90 to 90 lat
# Resolution: 100 m/pixel
# 16-bit, 1 band
python gdalSize.py -180 -90 180 90 100 16 1 mars_reference.tif

Output:

49152000.0 in Megabytes
46.9 in Gigabytes

Use Cases

• Storage planning - Estimate disk space before processing
• Data ordering - Calculate download sizes
• Processing planning - Determine memory requirements
• Cost estimation - Calculate cloud storage costs

Limitations

• Calculates uncompressed size only
• Actual compressed size varies by format and compression
• Does not account for tile/block overhead

For compressed size estimates:

• GeoTIFF with LZW: ~30-50% of uncompressed
• JPEG2000: ~10-20% of uncompressed
• Cloud-optimized formats: add ~5-10% for overviews

---

gdal2AsciiLatLonBands.py

Exports raster band data to ASCII/CSV format with optional latitude/longitude or XY coordinate columns.

Usage

python gdal2AsciiLatLonBands.py [-srcwin xoff yoff width height] [-band N] [-addheader] [-printLatLon] [-printYX] srcfile [dstfile]

Parameters

srcfile · string · required

Input raster file

dstfile · string

Output ASCII/CSV file (writes to stdout if not specified)

Options

-srcwin xoff yoff width height · integers

Extract subset window (offsets and dimensions in meters)

-band N · integer

Band number to export (can be specified multiple times for multiple bands). Defaults to band 1.

-addheader · flag

Add header row with field names

-printLatLon · flag

Include Lat/Lon columns (uses GDAL projection to calculate)

-printYX · flag

Include Y,X columns in meters

Examples

Basic Band Export

# Export band 1 to stdout
python gdal2AsciiLatLonBands.py input.cub

Output Format

Without coordinates:

Band1
12.3
15.7
18.2

With header and Y,X:

Y, X, Band1
1000.0, 2000.0, 12.3
1000.0, 2010.0, 15.7
1000.0, 2020.0, 18.2

With Lat/Lon and multiple bands:

Lat, Lon, Band1, Band2, Band3
45.123, -122.456, 12.3, 45.6, 78.9
45.124, -122.455, 15.7, 48.2, 81.3

Use Cases

• Point sampling - Extract band values at specific locations
• Data integration - Create CSV for import to databases or spreadsheets
• Validation - Compare pixel values across different datasets
• Analysis input - Generate point clouds for statistical analysis

---

Common Workflows

Complete Slope Analysis Workflow

# 1. Calculate slope
python gdal_baseline_slope.py -baseline 5 input_dem.tif slope.tif

# 2. Generate statistics
python gdal_hist.py -stats -hist slope.tif > slope_data.txt

# 3. Create visualization
python slope_histogram_cumulative_graph.py -name "Site Analysis" \
  slope_data.txt slope_plot.png

Metadata Documentation Workflow

# 1. Generate metadata
python gdal2metadata.py input.tif fgdc_template.xml metadata.xml

# 2. Validate FGDC metadata
mp -e metadata.xml  # If USGS MP tool is available

# 3. Create HTML view
xsltproc fgdc-html.xsl metadata.xml > metadata.html

Data Planning Workflow

# 1. Calculate storage needs
python gdalSize.py -180 -85 180 85 100 16 3 reference.tif

# 2. Estimate processing time
# Use size estimate to calculate processing duration

# 3. Plan tile scheme
# Based on size, determine optimal tile size

Installation

Basic Installation

# Install GDAL and core dependencies
conda install -c conda-forge gdal numpy

Full Installation (All Utilities)

# Install all dependencies
conda install -c conda-forge gdal numpy scipy pandas matplotlib lxml

Verify Installation

# Test GDAL
python -c "from osgeo import gdal; print(gdal.__version__)"

# Test other libraries
python -c "import numpy, pandas, matplotlib; print('OK')"

Requirements Summary

Script	Python	GDAL	NumPy	Pandas	Matplotlib	lxml
gdal2metadata.py	2.7+	✓	-	-	-	✓
gdal_hist.py	2.7+	✓	-	-	-	-
slope_histogram_cumulative_graph.py	3.x	-	-	✓	✓	-
gdalSize.py	2.7+	✓	-	-	-	-
gdal2AsciiLatLonBands.py	2.7+	✓	-	-	-	-

Troubleshooting

ImportError: No module named 'osgeo'

Install GDAL Python bindings:

conda install -c conda-forge gdal

Metadata validation errors

Ensure:

• Input file has valid projection
• Template XML is valid FGDC format
• Longitude values are in -180 to 180 range

Histogram visualization fails

Check:

• Input file is tab-delimited
• Contains required columns: level, value, count, cumulative
• matplotlib backend is properly configured

Size calculation seems incorrect

Verify:

• Reference image has correct projection
• Bounds are in correct order (min before max)
• Resolution units match projection units

Author

Developed by Trent Hare and contributors at USGS Astrogeology Science Center.

License

Public domain (Unlicense) unless otherwise specified.