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Archive for May, 2017

Calibration Targets 5: Around the World

by Timothy Whitehead on May.23, 2017, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

This is part of a series on calibration targets. Today we are having a look at various calibration targets around the world.

We start in India at the Shadnagar campus of the National Remote Sensing Centre where there are some calibration patterns specifically for satellite calibration:


This site in India is the only calibration site we know of that uses colours.

This site near Zuunmod, Mongolia appears to have been repainted several times.


We don’t know why the angle was changed slightly in the last repaint.

At Salon-de-Provence, France, we find a basic four square pattern:

Next we have a more complex set of patterns at Mount ShongShan, China. One reference states that there are also two rows of squares near this site, each extending over 2 km but we failed to find them.

The Sjökulla Aerial Test Range, Finland was probably designed primarily for aerial photography, but can also be used by satellites.

In South Africa, there is a single white square near Pretoria:


Designed to be exactly 100 m on a side. We don’t know why it wasn’t aligned with the cardinal directions.

The pattern at Peng-Hu, Taiwan was repainted at a different angle:

There are presumably more around the world, but we failed to find a collection listing them all. Also, in many cases temporary patterns are used, using tarpaulins or, in the case of thermal imaging, metal sheets. You can even buy specially made patterns.

There seems to be no universal agreement on what measurement is ideal. We measured some of the squares and four-square patterns:

Zuunmod, Mongolia: Concrete square on which the pattern is painted – 120 m. Painted four-square pattern – 70 m.
Four-square pattern, Salon-de-Provence, France: 60 m.
Four-square pattern, Peng-Hu, Taiwan: 60 m.
White square near Dunhuang, China: 115 m.
Four-square pattern near Boutou, China: 96 m.
White square, South Africa: 100 m.
Four-square pattern, Stennis Space Centre, USA: 50 m.
Four-square pattern, CalVal facility, India: 140 m.

Also useful for calibrating satellites are a number of sites around the globe whose altitude, colour and temperature have been carefully measured. They are typically dried up lake beds in deserts as such areas tend to be very flat and have a consistent temperature for a given time of day and day of year, and have minimal cloud cover. You can find a collection on the USGS website that has been collaboratively measured by many countries around the world. We have included it in the KML below.

To find the above locations, download this KML file.

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The Peru Floods with Google Earth

by Timothy Whitehead on May.22, 2017, under 3D Models, Argentina, Australia, Brazil, California, Denmark, England, Germany, Google Earth News, Google Earth Tips, Google Sky, Google maps, Hawaii, Indonesia, Ireland, Italy, Japan, Kenya, Mexico, Natural Landmarks, Netherlands, Sightseeing, Street Views, USA

A couple of weeks ago we had a look at three different floods around the world, including Lima, Peru. However, the flooding in Peru was very extensive, so today we are looking at some other locations around Peru.

Here is a ‘before and after’ showing how the Moche River, which passes through Trujillo, Peru, created a new delta:

before
after

Moche River delta creation.

Further north we can see how the Chancay River grew significantly wider:

before
after

Chancay River. We are seeing it after the water has subsided from it highest levels.

Zooming out and using Landsat imagery, we can see some large areas that were completely flooded. They are naturally swampy areas, but we could not find this extent of flooding in older imagery, so we believe it to be quite unusual.

before
after

Left: Google Earth imagery composed of Landsat/Sentinel-2 mosaic. Right: Landsat image from April 4th, 2017.

To find the above locations in Google Earth, download this KML file. We have included an image overlay of the Landsat image. We have also outlined all the 2017 imagery we could find for Peru. If you come across any other 2017 imagery in the region, please let us know in the comments.

The inland parts of Peru drain into the Amazon basin. There was also significant flooding there, but it is rain forest, so it is unlikely that we will see any high resolution satellite imagery (too much cloud cover). It also seems probable that as the water flows towards the ocean we will see floods along the Amazon in Brazil later in the year.

The post The Peru Floods with Google Earth appeared first on Google Earth Blog.

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