Digital Geography

Accessing Landsat and Sentinel-2 on Amazon Web services

The cloud has made it easier to process large amount of data, and satellite imagery processing benefits from cloud processing too. One of the cloud services that offers access to satellite images, and abilities to process them in the cloud – no more need to download it to your computer and process it there – is Amazon Web Services. If you’ve never worked with cloud processing, getting started with AWS can be a bit daunting. This tutorial gives beginners an introduction to accessing satellite images – Landsat and Sentinel-2 – on AWS.

Mapalomalia: First web geological modeling platform

Mapalomalia lets geologists create and visualize 3D geological models from their browsers. It’s a free to use geological modeling platform. I hope people will use it to convey information about our planet that helps humankind to tackle big problems and at the same times makes geological modeling easier. I have developed it with input from many geologists, and by releasing it early I hope to receive more input from many more geologists. Just sign up here to start creating models.

Extracting information from Sentinel-1

SAR images can see through clouds and in darkness, and are therefore very useful for operational monitoring of our seas. Detecting ships, icebergs, wind patterns, and oil spills is daily business in Europe with the Sentinel-1 satellite. Want to see for yourself how to extract information from a SAR image? In this tutorial, we’ll use the SNAP toolbox for Sentinel-1 to extract information on the number of ships at sea.

Adding projection data to ENVI headers (GIMMS 3g example)

Once in a while you may need to take an unprojected file and add coordinate parameters to the header. Assuming you use ENVI, the hard way is to perform a reprojection via Image to Map registration in ENVI Classic. The easy way is to add the coordinate information to the header file. Here we assume you do not need to warp the file to an ellipsoid or datum. Here we use the example of GIMMS 3g data from the University of Maryland and NASA. Start by importing the data as a Binary file.   It is important to realize that…

Short Announcement: SRTM 1 Data Worldwide

The digital elevation dataset resulting from the SRT Mission in the year 2000 is probably the most widely used digital elevation dataset in the world. It was first released with a 90 at ground resolution in a more or less global level (56° S to 60° N). In 2014 the White House announced the release of the 30 m original solution dataset. So they released parts of the dataset one-by-one. Our author Christoph just mentioned an update via Twitter.

Short Announcement: Landsat 8 Data Users Handbook

Landsat 8 is the successful successor of Landsat 5/ Landsat 7. It was launched on February 11, 2013. Since then we saw a major increase in possibilities of getting access to the data and integrations in software packages. Now the USGS published an in-depth document to support the basic understanding for the Landsat 8 observatory and its science data products.

First images from recently launched Sentinel 2 satellite

The earth observation satellite Sentinel-2 with Sentinel-2A and Sentinel 2B was launched on June 23rd 2015 from space centre Kourou in French Guiana. The mission is part of the Copernicus mission by ESA. The liftoff was recorded by ESA and can be watched here. Sentinel will be a complement to the multispectral satellites of the Landsat mission and SPOT. All observation systems in combination reveal a higher temporal resolution by shifted orbits and large stripe widths (Sentinel: 290km). Sentinel has a repetition rate of 10 days, Landsat 8 of 16 days but in combination with Landsat 7 a 8 day…

Some ways to produce high-res DEMs – tools and data

Many of us use digital elevation models (DEMs) for a whole bunch of different applications. There are some standard products which everyone should know, like SRTM1, SRTM3, ASTER, GLOBE or ETOPO1 for the land surface or GEBCO for bathymetry. However, they have a relatively low resolution and are therefore not suitable for all purposes. During the last few years there has been a huge progress in producing much better DEMs, especially local ones, using a wide range of techniques like LiDAR, photogrammetry, image correlation, structure-from-motion (SFM) etc. Some of these techniques make use of powerful, but expensive equipment (e.g., LiDAR),…

GeoTiff compression comparison

In remote sensing you often have to deal with large datsets because their spatial or temporal resolution is high. A typical Landsat 8 scene clocks in at 0.7 – 1 GB and if you are trying to process satellite images for a continent or even the globe you’re easily looking at multiple terrabytes of input data. I am currently working with MODIS time series data, which will use about 4 TB of space even before any processing is done. Therefore I started looking into compression methods. One of the easiest ways to save space is by employing the compression methods some file…

SMAP – “Soil Moisture Active Passive” generates high resolution soil data

Since we are still in the International of Year of Soils , another Digital Soil Science post is ready. Some of you might already know that I’m addicted to soil. As a guy who works in the field of soil erosion modelling, any kind of soil data is interesting for me and some are quite relevant. Especially soil texture and soil moisture are very crucial values about predicting soil stabilization. I showed a global soil database in a previous post, which contains many high resolution soil data. But guess what: Some more soil data is coming. This time the datasource is…

DEM comparison: SRTM 3 vs. ASTER GDEM v2

Let’s get ready to rumble! No, just kidding. We are all excited about the recent message from the white house: SRTM “1” (1 equals 1 arcsecond, whereas 3 was indicating the 3 arcsecond a.k.a. 90m DEM) or the official title SRTM-2 will be available for free in the next months (orig. here, dg here). So why is it so important? Most DEM-interested people will answer: “Use the ASTER DEM if you need 30m!”. But let us have a closer look on both systems and how they perform.