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The Snows of Olympus, Part II

Jun 15, 2015

Here are some more maps from this same area, first focusing on the Acheron Fossae region of the h0037 tile.
I scale the elevation colourization locally:

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Below, I zoom in on several areas containing several Souness catalogued GLFs, using either colourized elevation, or shading in polygons with ln(K_head), ln(K_ext), and ln(K_ctx) greater than 12, 10 or 10 respectively:

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Souness catalogued GLF number 96 merits a closer examination to have a look what is going on with the polygon.
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 It looks a little to me like the glacier filled the crater before it receded downwards (large version)

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The Snows of Olympus

Jun 14, 2015

The HRSC tile h0037 is a monster, it covers a vast area, the image file is 17568 x 144800 at 12.5m resolution and topography is 4391 x 36200 at 50m resolution. See also data product footprint at Mars ODE.

It covers an area including the summit of the vast Olympus Mons mountain, the largest on Mars and the largest volcano on any planet of the solar system.

There are a few Souness glacier-like forms in the north of the tile, the name 'Nix Olympia' dates back to the time of telescopic observations which perhaps mistook the brighter rocks of the Olympus Mons massif for snow.


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The Snows of Olympus is also the title of a book by Arthur C. Clarke which I have, containing some speculation about colonisation and terraforming Mars, along with some computer graphics renderings which were state of the art in the early 1990s of a Mars undergoing terraforming.
The above image shows the Olympus Mons Lobate Debris Apron, which is in fact thought to be glacial in origin, at the very high obliquity epochs in Mars' past, glacial activity is believed to have occured in the tropical mountain regions around the Tharsis bulge.

The Souness glacier like forms are concentrated to the north of the tile however, and in neighbouring tiles h1210, h1232 and h5280.

The above image showed up a significant issue with the dissertation. The Bayesian classifier used the nadir image data, as well as the digital terrain model and derived topographic values. However looking at the h5280 field at 130W 45N it is clear the scaling of the image brightness is separate for each tile, which means it doesn't mean much in the context of global statistics.

In the more detailed images below, an equicylindrical coordinate system is used with a standard parallel at 40 degrees of latitude.


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Showing an area around 37N, 133W, in the Acheron Fossae region.

h1210 and h1232

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Revisiting my dissertation work on Mars

Jun 12, 2015

In my MSc dissertation at Aberystwyth University, I wrote about mid-latitude glaciers on Mars. I linked the 1309 candidate mid-latitude Martian glaciers published by Colin Souness with topographic data from Mars Express, and made derived topographic layers in GDAL and LandSerf. I made a layerstack of Mars Express images, topography and derived layers and segmented it in RSGISLib, and did some statistical processing to create a kind of naive Bayes classifier to indicate which areas have similarity in topography to the Souness glaciers.

Due to time and space constraints, I did not actually present full results on all of the 179 HRSC tiles within the dissertation. I had intended to do some more afterwards, but at one point my external hard drive failed and I had to re-download some of the data.
A figure from my dissertation with colourized MOLA elevation, overlaid on a Mars Orbiter Camera wide-angle mosaic images by transparency, showing the general area. Unfortunately I lost the MOC images and spent some time trying to reproject them again correctly since, and I kept getting an offset between it and the other data. Fortunately there is a version available from the USGS that has already been put into the same projection as MOLA.

In the dissertation, I calculated the distribution of the various variables, both for the whole of the HRSC data tiles I used, and for the areas coinciding with the locations of the Souness glaciers. By comparing the two, a Bayesian classifier is derived.

The head, extent and context areas are explained in the dissertation, the head simply being a small circle around the location of the glacier head as recorded in Souness, the extent being calculated from the width, head, centre and foot recorded, and the context is the extent polygon expanded by 3 times.

I present results from two tiles which were written about in the dissertation, h0248 and h2279, but will be expanded on a little below.

update (13/06/15)

I have corrected an error in the classification script that gave spuriously small values of the 'Extents' classifier function, and revised it to take the nadir image data out of the classifier, since it is scaled separately for each tile, it doesn't make a lot of sense to consider it in the context of global statistics.


larger version (25m/pixel)
Tile h0248
The region near the bottom of the image shows a number of Souness glaciers, which are in an area which is indicated by the classifier, however there are several regions that are indicated by the classifier which do not have any Souness glaciers. There are other glacial features such as crater fills that were beyond the scope of Souness's catalogue, which focused on forms analogous to valley glaciers on Earth.


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Tile h2279
Again, a number of Souness glaciers are shown, which have a high classifier value but regions with high values exist that do not have any Souness catalogued objects.
The classifier functions are clearly not specific to the Souness catalogue type glaciers, but may indicate general areas where glacial forms occur, or possibly areas where glacial forms existed in the past.

Remote Sensing and GIS links page

Jun 9, 2015

Some time ago I posted a links page, I have added some more and rearranged it a bit:

Remote Sensing sensors and data:

  • Landsat home page at the US Geological Survey.
  • NASA Landsat Science page.
  • US geological survey Earth Explorer interface for accessing Landsat (and other) satellite data.
  • ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) homepage. ASTER is an imaging instrument onboard Terra, the flagship satellite of NASA's Earth Observing System (EOS).
  • information on TERRASAR-X (Synthetic Aperture Radar satellite).
  • The SPOT series of commercially operated optical high-resolution multispectral satellites.
  • The European Space Agency's Copernicus programme (previously known as the Global Monitoring for Environment and Security programme (GMES)), including the current and upcoming Sentinel series of Earth observation satellites.
  • Including information on the Worldview series of satellites.
  • In 2000, the Space Shuttle flew a radar that produced a digital elevation map of the world. The 1 arcsecond data from that is now available for most of the world, previously only the USA had 1 arcsecond data publicly released, with the data covering the rest of the world released at 3 arcseconds resolution. Since September 2014, the 1 arcsecond data has been released for most of the world.

Earth-based Applications of Remote Sensing and GIS

Planetary Science Applications

Astronomy links

  • On August 21, 2017, millions of people across the United States will see nature's most wondrous spectacle — a total eclipse of the Sun. It is a scene of unimaginable beauty; the Moon completely blocks the Sun, daytime becomes a deep twilight, and the Sun’s corona shimmers in the darkened sky. This is your guide to understand, prepare for, and view this rare celestial event. March 20th 2015 eclipse in Faroe Island and Svalbard.
  • A website that details the passes of the International Space station, Iridium flares and other artificial satellites, as well as providing information on planets etc. visible in the sky.
  • Free planetarium software. The program enables you to draw sky charts, making use of the data in many catalogs of stars and nebulae. In addition the position of planets, asteroids and comets are shown.
  • Solar Eclipse prediction software, which shows the track of the moon's shadow on the Earth, and local circumstances including magnitude, start/end times and duration of totality for eclipses between 13000BC and 16999AD. Also see LmapWin for lunar eclipses.

Remote Sensing and GIS software, tutorials etc.

  • Dan Clewley's blog on open-source remote sensing software.
  • Online access to ArcGIS Help.
  • QGIS project page where you can find the free and open source QGIS software.
  • A self-paced course on free & open source software for geospatial (FOSS4G) applications from the Free and Open Source Software 4 Geo Academy. 5 self-paced courses using QGIS (and a bit of GRASS7) are available.
  • QGIS blog by QGIS developer and data visualisation specialist Anita Graser.
  • A GIS blog containing tips and tutorials on QGIS.
  • Blog by Luca Congedo, the author of the Semi-Automatic Classification Plugin for QGIS that allows for supervised Land Cover classifications.
  • This reference manual details the use of modules distributed with Geographic Resources Analysis Support System (GRASS), an open source (GNU GPLed), image processing and geographic information system (GIS).
  • Carleton University Open Source GIS tutorials.
  • a free and open source program to manage GPS data. This can import data from a GPS device and add map layers from OpenStreetMap and digital elevation model data.
  • GIS information portal.
  • Online converter in Javascript from Lat/Long to OSGB grid references and vice versa.
  • -Downloadable Grid Inquest software from the UK Ordnance Survey to convert between Lat/long and OSGB grid references. An online batch converter is also available.
  • An online database of spatial reference descriptions in a large number of geographic and projected coordinate systems.
  • Flex Projector is a freeware, cross-platform application for creating custom world map projections. The intuitive interface allows users to easily modify dozens of popular world map projections - the possibilities range from slight adjustments to making completely new projections. Flex Projector is intended as a tool for practicing mapmakers and students of cartography.
  • free open source image analysis software.
  • Geomorphons are a pattern recognition method of terrain analysis developed by Tomasz Stepinski and Jaroslaw Jasiewicz. It is available as a Web-based utility that allows users to calculate geomorphons maps from their own DEMs (for smaller datasets) and also as a GRASS7 module. Blog post including video of lecture about it.
  • Written by Prof. Jo Wood, LandSerf is a freely available Geographical Information System (GIS) for the visualisation and analysis of surfaces. Applications include visualisation of landscapes; geomorphological analysis; gaming development; GIS file conversion; map output; archaeological mapping and analysis; surface modelling and many others. It runs on any platform that supports the Java Runtime Environment (Windows, MacOSX, Unix, Linux etc. I used it myself in my dissertation on Martian glaciers.


HTML, CSS and Javascript

Online Mapping

Downloadable GIS data

Cartography and Data Visualisation Advice

Google Fusion Tables

GIS Data visualisation examples

General Mapping Fun

  • a lot of interesting things done with maps. warning: procrastination alert.
  • warning: procrastination alert.
  • A website (in German) with many examples of historical maps, including many examples of the Soviet Union's military maps at 1:500k and 1:1M scale, and among other things maps with various European powers realised as animals (often this is 1st world war propaganda - from all sides).
  • A business based in Cornwall, offering quality cartographic and design services on a contract basis for clients of all sizes.

Travel time maps

LaTeX (Document processing)

Art/Science collaboration

  • by Julian Ruddock. Website showing his projects that are based on art and science collaboration in relation to climate change.

Citizen Science and crowdsourced cloud computing


Galactic Information Systems

Jun 8, 2015

This is the result of georeferencing an image of the Andromeda galaxy (M31) using the QGIS Georeferencer plugin. First flip the image horizontally, because celestial right ascension coordinates go the opposite way round to longitudes, because we are inside the celestial sphere.
Then with the aid of a star chart, find a few reference points, and use SIMBAD to find coordinates for then. I used the M31 centre, the satellite galaxies M32 and  M110, and the stars 35 and 32 And.
The result was that M31 is just off the coast of Italy.
The distance of M31 is approximately 780 kiloparsecs, 1 parsec being 3.09x1016m. 1 degree on the sky corresponds to 13.6kpc at M31's distance (note that the stars in the image are Milky Way stars and much closer) and that means that 1 metre on the ground translates to 0.4 light years in M31.
Therefore the density of stars in M31 is perhaps similar to the corresponding density of trees in a forest, except of course that the stars are arranged in a 3 dimensional structure, and the stars themselves are vastly smaller then the corresponding trees, the Sun's diameter at M31 distance corresponding to about 0.7mm on the Earth, the size of a small insect.

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