Satellite imagery updates for 2015

For the first half of 2015, as it has in the past, Google released imagery update maps showing outlines of newly updated imagery. However, in June, it released the Voyager layers, which include a ‘satellite imagery updates’ layer. We believe the change was made due to the deprecation of Google Maps Engine, which is what was formerly used to publish imagery update maps. However, the Voyager layer has only been updated once since June, so we have mostly been relying on the Google Earth API to find imagery updates. See here for our imagery update posts of 2015.

We have used the Google Earth API to create an approximate map of the areas in Google Earth that currently have imagery dated 2015.

To see the above map in Google Earth download this KML file.

The USA, parts of Europe, and Japan got quite a lot of aerial imagery. Most of the rest of the world got satellite imagery concentrated on areas with high population. Interestingly, the southern and eastern countries of Asia got remarkably good coverage.


Also of note, is that Syria and the Ukraine seem to have been added to the list of countries with blanket censorship. There were no satellite imagery updates with imagery dated 2015 in Syria, the Ukraine, Afghanistan, or Iraq. Both Syria and the Ukraine did receive imagery during 2015 but it was dated 2014. It is not Google carrying out the censorship but has most likely been done by buying rights to the imagery from the satellite imagery providers. The censorship in Ukraine was implemented long after the conflict there started and we have seen imagery taken after flight MH17 was shot down over the Ukraine. The most recent imagery appears to be from November 2014. At the same time, the Ukraine got Street View in October 2015, so although it is censored from above much of it is now more visible from ground level.

It must be noted that Google has not yet added any December imagery, and in general Google’s imagery updates often include imagery of various ages, so the amount of imagery dated 2015 will increase with time.


About Timothy Whitehead
Timothy has been using Google Earth since 2004 when it was still called Keyhole before it was renamed Google Earth in 2005 and has been a huge fan ever since. He is a programmer working forRed Wing Aerobatx and lives in Cape Town, South Africa.

Source: Google Earth Blog

Seeing a tornado track with Landsat imagery

We have looked at the paths of destruction caused by tornadoes in Google Earth imagery a number of times before. Nearly every one of the tornadoes we have looked at in the US occurred in the months of April or May, which appears to be peak tornado season in the US. Tornadoes can, however, occur at any time of year and due to the unseasonably warm weather the US has been having recently there were several tornadoes just before Christmas.

We came across this story, which says that one of the tornadoes had a record long track for the month of December. Google has not yet released any December imagery so we wondered if it would be visible in Landsat imagery. We used the technique described in this post to get a relatively low resolution Landsat image of the area captured on December 24th, the day after the tornado struck and found we were able to just make out the path of the tornado. We also downloaded the higher resolution version of the Landsat data and processed it with software from GeoSage as described in this post.


We were able to trace out the path of the tornado a distance of around 92 km (57 miles). News reports, however, mention damage to property quite some distance from both ends of the visible track (from Clarksdale, Mississippi to Lutts, Arkansas) reaching at least double that distance.

A section of the track as seen in Landsat 8 imagery. Can you see it?

Keep in mind that Landsat imagery has a resolution of about 30m per pixel. The visible track of the tornado is over a kilometre wide in places.

Shown above is only a part of the visible track. For the full track and two different versions of the Landsat imagery (cropped and compressed to keep the file sizes down) download this KML file. The KML also includes markers relating to some news stories and links to YouTube videos of the tornado or other tornadoes in the vicinity.

About Timothy Whitehead
Timothy has been using Google Earth since 2004 when it was still called Keyhole before it was renamed Google Earth in 2005 and has been a huge fan ever since. He is a programmer working forRed Wing Aerobatx and lives in Cape Town, South Africa.

Source: Google Earth Blog

GIS plays critical role in US telecommunications planning & security

By Kristen Davis


The U.S. faces thousands of national security threats each year; in case of emergency, it's imperative that our wireless telecommunication systems are active and defensible. For that reason, the Institute for Telecommunication Sciences, the research and engineering laboratory of the National Telecommunications and Information Administration, an agency of the U.S. Department of Commerce, provides propagation models essential to wireless communications planning to a number of government agencies.

ITS has been providing radio wave propagation predictions since before World War II, but times have changed. Since accurate geographic information is critical for developing accurate propagation models, ITS more recently developed propagation modeling website tools that use commercial geographic information systems to both acquire geographic data and display geographic coverage areas.

Previous propagation modeling programs required government users to have a concrete understanding of radio propagation and prediction concepts, but many of these models were ported to new programs that operate in a Windows® environment and integrate with the proprietary Esri™Geographic Information System program most commonly used by its sponsor agencies. This implementation only requires users to install licensed commercial software and have some expertise in the use of that software.

But times have changed again. The federal government has created a digital strategy, establishing, among others, the goals of making existing high value data and content available through web APIs, and using a shared platform approach to develop and deliver digital services in order to lower costs and reduce duplication. So, seven years ago, with assistance from Department of Defense sponsors, ITS began developing a new generation of web-based GIS solutions for propagation prediction. Now ITS disseminates software applications that reduce dependency on licensed software applications, allowing end users to access the models through a web interface, the Propagation Modeling Website. The PMW uses commercial GIS to both acquire geographic data and display geographic coverage areas. It covers radio frequencies from 1 MHz to 20 GHz.

The PMW login screen is shown in Figure 1. Users can log into a central server to perform propagation analysis, storage and retrieval. PMW includes the capacity to perform propagation analysis using any of the following propagation models: TIREM 3.15; Longley-Rice 1.22; COST 231 Extended Okumura-Hata; Undisturbed Field/Mobile-to-Mobile; and ICEPAC. Propagation analyses, using all five models, can be performed in either single or batch transmitter mode using a separate thread for each analysis.

Figure 1. Users log into a central server via this PMW log in screen.

Users can export propagation analyses in .kmz format as well as GIS shape or Esri layer files, for use with Google Earth or another GIS such as Esri’s ArcGIS for Desktop application. Figure 2 shows an example of field strength studies from four of the five models, exported from PMW and imported into Google Earth.

Figure 2. This field strength study uses the Longley-Rice model for a transmitter located southwest of Boulder, Colorado. The analysis was run in PMW, then imported into GoogleEarth.

In single analysis mode, users can geographically select a transmitter from an embedded interactive map display. In batch mode, users can load an Excel transmitter file and plot the desired transmitters on the map prior to running the analysis. This functionality was developed using open source products OpenStreetMap and OpenLayers.

The PMW is delivered with five zoom levels for the map, which translates roughly to a scale of 4,888 meters per pixel. The PMW is shipped with additional zoom levels up to 12, or a scale of 76 meters per pixel. OpenStreetMap provides 20 zoom levels to achieve a scale of 0.298 meters, but rendering each tile for 20 zoom levels would result in a storage requirement of 54 terabytes. Figure 3 shows the web map zoomed to level 12. The reason for packaging and shipping the geographic data with the software is that many PMW users operate in a secure environment and cannot connect to the internet to dynamically update the data.

Figure 3. The embedded web map shows the geographic location of proposed transmitters.
The PMW is currently customized to fit the needs of ITS’ sponsors, which include several DoD agencies and the National Weather Service, and is available only to U.S. government agencies. To meet the different security needs of defense and civilian agencies, the solution can be implemented either on an agency’s own secure intranet or on an ITS-hosted secure website. Because the PMW is extremely modular in design, as new sponsors join the project the PMW can grow to fit additional needs and requirements. For example, NWS uses the tools to map radio coverage to U.S. population, to ensure that its All-Hazards Emergency Messages will reach at least 95% of the population. DoD agencies might use the tool for tasks like planning the location and density of transmitters and repeaters for new or ad hocsecure communications networks.

The PMW solution integrates commercial, off-the-shelf GIS, database and web-development products in a fully customizable analysis environment that can be tailored to meet individual customer needs. The solution was designed to be cost efficient, modular and scalable. It operates in a Windows environment, using widely available tools and utilities. Users can access the models from virtually any desktop or laptop through a browser interface. Hardware used in the development of the PMW included a dual quad-core web development machinewith 32 GB of RAM. The software included: Windows Server 2008 R2, Esri ArcMap 10.1, Visual Studio 2010, SQL Server 2008, .NET 4.0 and IIS 7.5.

Due to the large selection of GIS databases available, customer agencies can choose to include terrain, satellite and aircraft imagery, ground transportation infrastructure, building data and/or population distribution. By developing PMW, ITS has provided system tools to help government agencies efficiently manage their telecommunications infrastructure through sound system planning and interference detection for national security and public safety.

The Institute for Telecommunication Sciences supports its parent agencies by performing the research and engineering that enables the U.S. government, national and international standards organizations, and many aspects of private industry to manage the radio spectrum and ensure the advancement of innovative, new technologies. ITS also serves as a principal federal resource for solving telecommunication issues for other federal agencies, and state and local government. Certain commercial products are identified in this article to adequately specify the technical aspects of the reported modeling solution. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the products identified are the best available for this purpose.

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