Tag Archives: Google Earth

A Brief History of Google Maps…and a not so Brief Video

In this long but useful presentation from 2012 Google Maps vice president Brian McClendon and colleages provide a detailed overview of the platforms evolution. Some of the key points are summarised below.

In the mid 90s Silicon Graphics developed the ‘Space-to-Your-Face’ demo to demonstrate the power of their Onyx Infinite Reality CGI workstation. In the demo the view zooms from orbit to the Matterhorn via Lake Geneva, using a combination of satellite, aerial imagery and terrain data. This is included in the Silicon Graphics showreel from 1996 which be viewed on YouTube here.

In 2001 the company Keyhole was founded as a startup providing mapping for the travel and real estate industries on the basis of a subscription model. After achieving wider recognition through use by CNN during the invasion of Iraq in 2003, the company was subsequently acquired by Google in 2004.

At the same time Google were working on the creation of Google Maps which used a combination of client side processing via AJAX and pre-rendered map tiles to enable its highly interactive and smooth scrolling slippy map system. However, now that network bandwidth and processing power has been increased Google Map tiles are no longer pre-rendered and are instead provided on demand.

Between 2005 and 2008 Google Maps licensed further data to obtain a full world map with more comprehensive coverage. At the same time Google were also working to acquire high resolution imagery.

Street View started in five US cities in 2007 but had expanded to 3000 cities in 39 countries by 2012. In 2008 Google released Map Maker to capture data where other basic mapping data and Street View were absent.

Google’s Ground Truth project now enables them to generate their own maps from raw data by combining satellite and aerial imagery with road data and information capture via Street View. This data is processed with an application callled ‘Atlas’ that Google developed internally. With the aid of advanced computer vision techniques they are able to detect and correct errors and extract further contextual information from the raw imagery data that helps them make their maps more complete and accurate. This includes details as specific as the names of streets and businesses appearing on signs.

Corrections are also crowd-sourced from users with the aid of their ‘Report Maps Issue’ feature. Staff at Google are then able to verify the issue with Street View, edit the map and publish the corrections within minutes.

The presentation moves on to further discussions on ‘Google Maps For Good’ and their work with NGOs (19:20), ‘Google Maps for Mobile’ and the provision of offline map availability (27:35), the evolution of the equipment used to capture Street View (31:30), and finally the evolution of their 3D technology (37:40). The final discussion in particular reiterates the content in my post yesterday from a slightly different perspective.

What I found particularly interesting in this video was the continued manual intervention via Atlas but also the extent to which they are able to gather contextual information from Street View imagery.

3D Imagery in Google Earth

Since 2006 Google Earth has included textured 3D building models for urban areas. Initially these were crowd-sourced from enthusiastic members of the user community who modeled them by hand with the aid of SketchUp, sold to Timble in 2012, or the simpler Google Building Maker, retired in 2013. As the video above shows, from 2012 onward Google have instead been using aerial imagery captured at a 45 degree angle and employing photogrammetry to automate the generation of 3D building and landscape models.In the following video from the Nat and Friends YouTube channel Google employees help explain the process.

As explained Google Earth’s digital representation of the world is created with the aid of different types of imagery. For the global view 2D satellite imagery is captured from above and wrapped around Google Earth’s virtual globe. The 3D data that appears when users zoom in to the globe is captured via aircraft.

Each aircraft has five different cameras. One faces directly downward while the others are aimed to the front, back, left and right of the plane at a 45 degree angle. By flying in a stripe-like pattern and taking consecutive photos with multiple cameras, the aircraft is able to capture each location it passes from multiple directions. However, the need to obtain cloud free images means that multiple flights have to be taken, entailing that the images captured for any single location may be taken at different times days apart. The captured imagery is colour corrected to account for different lighting conditions, and the images for some areas even have finer details like cars removed.

The process of photogrammetry as employed by Google works by combining the different images of a location and generating a 3D geometric surface mesh. Computer vision techniques are used to identify common features within the different images so that they can be aligned. A GPS receiver on the aircraft also records the position from which each photograph was taken enabling the calculation of the distance between the camera on the plan and any given feature within the photograph. This facilitates the creation of depth maps which can be stitched together using the common features identified earlier to form a combined geometric surface mesh. The process is completed by texturing the mesh with the original aerial imagery. For regularly shaped objects like buildings this can be done very accurately with the aid of edge detection algorithms that can identify the edges of buildings in the imagery and help align them with the edges of features in the mesh. For organic structures this is more challenging.

Google Earth includes imagery for may different levels of detail or zoom. According to the video the number of images required is staggering, in the order of the tens of millions. While the zoomed out global view in Google Earth is only fully updated once every few years the aerial imagery for particular urban areas may be updated in less than a year. Gathered over time this imagery can enable users to observe changes and this can be leveraged for analysis with the aid of Google’s Earth Engine.

Pigeon Sim with Leap Motion

Of all the demos developed here at CASA Pigeon Sim remains a firm favourite. Using a Kinect to capture body movements the simulator allows the user to fly and flap their way around London in Google Earth. What I didn’t know is that it also has a mode for Leap Motion. Steven Gray who teaches Big Data Analytics at CASA demonstrates how to use it in the video below:

If you want to give it a try the full Pigeon Sim code repository is available on github. In order to run the Leap Motion version you should only need to download the contents of the ‘web_client’ folder. Open the ‘index.html’ file in your web browser and then add ‘?enableLeap=1’ (e.g. web_client/index.html?enableLeap=1) to the search query in your browser. Happy flapping!

Google Earth Pro is Free to Download

I recent learned via the Google Earth Blog that Google Earth Pro is now free to download. I hadn’t used Google Earth for some time so I decided to try out the Movie Maker feature which is Pro only.

With movie maker it is possible to record live navigation with the mouse although this doesn’t tend to give a very smooth or or professional result. Using a specially designed 3D mouse such as the Space Navigator works much better. For my test I opted to make my video from a quick tour I created zooming into the Tower of London from orbit. This was achieved by selecting a sequence of points for the camera to visit. Movie Maker was then used to convert that tour to video. This took about 30mins to render with a fade in and fade out added in Adobe Premiere.

The attribution details at the bottom of the screen can be a little distracting because they change as the view moves between imagery from different satellites. It would be possible to crop these out but Google do insist on particular guidelines for permission to use their imagery and attribution. The are also occasional issues where parts of the 3D geometry flicker due to caching. Nevertheless, the results are very good for a quick and easy visualisation!

The combination of satellite imagery and 3D geometry are great for engaging viewers and giving a map context. Other features like a recorded voice over and the ability to highlight areas of interest can also be useful depending on the context. A comparison of features between the free and Pro versions of Google Earth can be found here, along with the link to download it.