DLR’s new Global Urban Footprint (GUF) data is now available at the Urban Thematic Exploitation Platform (U-TEP)! Use this opportunity to inspect the entirety of urban and rural human settlements in a so far unique precision and consistency.
Satellites enable continuous mapping of Earth’s surface. They allow analysts to record the expanses of cleared forests, lost agricultural land and constructed settlements. But until now, the perception of inhabited areas has lacked a spatially detailed and consistent global view; populated areas and those used for infrastructure are frequently hard to distinguish in optical satellite images. Scientists at the German Remote Sensing Data Center (DFD), part of the DLR Earth Observation Center (EOC), have succeeded in using a newly developed method to map the world’s cities at an unprecedented spatial resolution. A fully automatic image analysis system has used radar data to create a global settlement mosaic – the ‘Global Urban Footprint (GUF)’.
Over 180,000 images acquired by the German radar satellites TerraSAR X and TanDEM X between 2010 and 2013 were processed, together with additional data such as digital terrain models, to produce the GUF. In all, the DLR team processed more than 20 million datasets with an input volume of more than 320 terabytes which is equivalent to the information contained on roughly 460,000 compact discs. The procedure also included an automated quality assurance check aiming to ensure maximum accuracy – a prerequisite for the reliable derivation of spatial metrics and indicators on urbanization patterns and trends. The team applied sophisticated algorithms in a complex decision-making process to assign each of the roughly 50 billion pixels of the input imagery to one of two coverage types: settlements in black and any other land surface in white. This focus on just two categories clearly highlights the settlement patterns, improving the ability to analyse and compare them with other urban built-up areas across the world. Unlike previous approaches, this fully automatic analysis procedure detects the characteristic vertical structures of human habitations – primarily buildings. In contrast, areas used for infrastructure purposes are not mapped. This is why broad urban canyons or expanses of greenery within the cities are shown as white corridors and patches in the GUF layer.
The GUF delivers unparalleled precision. Until now, global analyses based on Earth Observation data have been unable to identify small villages. Now the black-on-white GUF map is a portrait of the human presence on Earth in the year 2012, to a maximum spatial resolution of 12 m, sometimes covering even single houses. Starting this month, the GUF dataset is freely accessible via our online U-TEP portal at full spatial resolution of 12m for scientific use, along with an easier to handle 84m version for any non-profit use.
The new GUF dataset and the newly developed evaluation method help to acquire a better understanding of the urbanisation phenomenon and hence, in future, to respond appropriately to the immense social challenges of mushrooming cities, population explosion, climate change and the erosion of biodiversity. By improving the quality of spatial analysis and modelling, users benefit from the increase in the precision of data relating to settlement structures. Planning agencies and development banks are also important clients of these new data and technologies. For instance, uniform data – applicable worldwide – on the location of settlements and including important parameters on their sizes and shapes, and also their compactness, help with the derivation of important information of a kind urgently needed in infrastructure planning. This is a crucial advantage, especially in remote and underdeveloped regions of Earth, where suitable geographical data are frequently scarce.
From now on the U-TEP team will constantly add new valuable products and services required for urban management and monitoring. To get more information, check the U-TEP product and service portfolio envisaged for the first implementation phase of our project as well as the U-TEP App Store and stay tuned!