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greenland_980

October 27, 2015
by chris
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Greenland mosaic

Until now my collection of Landsat based image mosaics of the Arctic islands missed the big one, i.e. Greenland. I am happy to announce now this is being addressed and you can now get also a Greenland mosaic:

This is by far the largest Landsat mosaic i produced to date with nearly 20 gigapixel size. Size in general is not really an issue but Greenland offers a number of challenges for mosaic assembly.

Landsat coverage is incomplete and the northern edge of the covered area produces a number of problems in addition to the lack of data beyond 82.66 degrees latitude. In general the Landsat satellite is in a sun synchroneous orbit so it covers areas at the same local time and therefore approximately the same lighting everywhere on Earth. At higher latitudes this time slot however more and more shifts away from the morning timeframe of lower latitudes and due to the overlap between different satellite orbits you end up with images with illumination varying quite a lot even if they come from the same time of the year which is difficult to assemble seamlessly.

Another problem are contrails. Most flights between Europe and North America cross Greenland and southern Greenland therefore is a fairly busy area is the sky. Planes frequently produce contrails that are often well visible in satellite images but are pretty hard to detect and remove like in the following example from one of the source images.

And finally there are of course the usual problems of assembling images for Arctic areas which – due to the size – vary quite a bit between the different parts of the island. Essentially there are at least five opimization criteria for image assembly:

  • snow minmum – you want the image with the least seasonal snow in the non-glaciated areas
  • sun elevation – you don’t want the sun to be too low so you don’t have overly long shadows
  • vegetation maximum – you want to catch the maximum of the sparse vegetation
  • sea ice and lake ice minimum – you want the least amount of ice on lakes and the sea
  • thawing maximum – you want the glaciated areas to be shown at the thawing maximum so melt pools and other ice surface structures are well visible

All of these occur at different times at the same place and most vary significantly depending where on Greenland you look. In most cases these occur some time in August although thawing maximum is frequently already in July and sea ice minimum in early September. And of course clouds will frequently spoil things in any case.

As usual you can find more information and sample images on services.imagico.de. If you like to use this mosaic let me know.

October 11, 2015
by chris
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Map design economics

I apologize for the potentially misleading title – many will likely assume this is about selling design but actually what i want to write about here it is more about buying design.

The idea for elaborating on this subject came from seeing the recently introduced Wikimedia maps, in particular its appearance at the lower zoom levels

which is a great example of map design going wrong and seems also well suited to explain the causes why this happens in maps today.

I should probably add upfront: i am not involved in the development of Wikimedia maps nor do i have any particular investment or interest in this project and although i point this out as an example of quality problems in map design here it is just an example and does not represent a case of particularly bad quality – you will be able to find many similar examples in other maps.

What the example above shows is quite simply bad map design. This is not limited to this particular map scale, you can still observe the same as you zoom in several levels but it is most obvious at this scale. One of the most basic rules of good map design is to give the map user a correct and consistent impression of reality. Note i do not say realistic here. A map is not a photograph but an abstract depiction – this depiction is however still meant to show reality. This means if you depart from creating a faithful depiction you should always do so deliberately and consciously and your aim has to be to avoid creating a misleading impression on side of the map user.

If a map design no more tries to correctly and consistently depict reality it essentially looses its raison d’etre and becomes a piece of pure art – if it qualifies as such – or simply a pile of digital junk.

Now at the scale of the map above this is not easy – there is not much room to show the complexity of reality but it should be obvious that you can do much better than showing the baltic sea as several unconnected lakes or Japan as a peninsula. The standard OSM map style – though certainly not great in that regard – is obviously doing a much better job.

As many of the readers probably know i am fairly familiar with this particular design problem, i.e. consistently representing coastlines and waterbodies at coarse map scales but i am not writing this to promote my work on this subject. Any approach to this problem is full of subjective choices and any map designer is free to use a different approach here but it is essential to actually make conscious design decisions and not just render the random results coming out of the arbitrary combination of various algorithms.

So much about the problem from the perspective of map design but my actual subject today is what causes these problems to prominently appear in maps intended for a broad audience.

Although Wikimedia is not a company it works quite similar to a commercial enterprise when it comes to executing a map development project. What happens is that the decision is made that a map is to be developed and people within the organization, hopefully mostly those competent on the matter, are tasked with coming up with specifications of the requirements for this map.

Here the problem usually starts because it is inherently difficult to put design aspects into a project specification. There are essentially two ways this is done:

  • specification by example – the map design should be in certain aspects like some existing reference design. This method has two major problems: (a) it only works for standard products and not for new, innovative or uncommon designs and (b) in many cases – either due to internal policies or by law in cases of public institutions and involvement of tax money – it is not allowed to do this because the specification based on an existing product is not neutral.
  • specification through technologies used – instead of specifying the design itself it is only specified what technological means are supposed to be used in creating this design. Essentially this is a bit like comissioning a portrait painting and specifying it is supposed to be painted using water colors.

Given the constraints of the first method the second approach is by far the most common method to address design aspects in map specifications. It is probably clear that practically this rarely ensures a certain level of quality in design and it can even be counterproductive in a lot of cases. In the Wikimedia maps example the technical requirement to use a vector tiles approach (which was likely part of the specification) for example leads to the need to massively reduce the data volume for the lower zoom levels which is done in a way that adversely affects the rendering results. Without knowing the actual specifications for the Wikimedia maps it is a safe bet that these do not contain any requirements regarding the consistency in waterbody appearance at all.

On a more general level the problem here is that maps are created to fulfill certain economic needs. Maps address these needs through design and design is enabled by technology. This mechanism is not specific to maps, it is universal to all fields of design. In case of modern digital map design however technology has a much higher significance on what is possible and can be efficiently accomplished than in other, more conservative design disciplines.

The problem is that this mechanism is often not respected in the way decisions are made – it is ignored that design is the central link allowing technology in maps to address economic needs and instead it is often assumed that implementation of technology somehow magically leads to fulfillment of the economic goals. Traditionally people say what is possible design-wise is usually limited by what can be done technologically but in map rendering i have the strong impression at the moment that often use of many readily available technologies is constrained by the limited founding available to design in map projects since budgets often essentially end at the technical level.

For solving this problem it probably helps to look how other fields in design deal with this matter. If you look at how projects are managed in the fields of architecture and industrial design you can see that drafts have a much higher importance there. They can range from simple concept sketches to detailed design plans. It is common to make design decisions based on competing drafts by several designers developed independently to ensure a wide range of possibilities is taken into account and to give new and innovative ideas a chance.

I have never seen this happening in a commercial digital map design project. It is of course common to try different design variations during development but having several completely independent drafts made would be extremely unusual. You can of course argue that architecture and industrial design with total budgets often several orders of magnitude larger can afford paying for several drafts that are not used in the end while map design projects cannot – there is certainly some truth to that but even in those fields people usually do not have money to burn but spend the money in ways they think will ultimately turn out to be good investments.

sval_3d_980

September 22, 2015
by chris
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3D views Svalbard

Supplemental to the Svalbard mosaic here some 3d views of the area created using this and elevation data from the Norwegian Polar Institute (CC-BY-4.0 license).

The NPI data is detailed but quite outdated in large parts – here a map of the major coastline changes between that data and the currect state (blue is coastline recess, mostly due to glacier retreat, orange is advance).

svalbard_980

September 8, 2015
by chris
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Svalbard mosaic

After previously showing Landsat mosaics of islands in the arctic i now also completed an image of the Svalbard archipelago.

Compared to the islands of the Russian Arctic Svalbard is more difficult since is features much more variable and less stable weather. The large temperature contrasts of the ocean water between the east and west side of the islands lead to frequent formation of clouds and weather situations where at least a large part of the islands is cloud free are very rare, especially in summer. Also summer snowfall is quite frequent so it is more difficult to find images depicting ideal conditions. While Svalbard could be fully covered with just about ten Landsat scenes this mosaic is based on 77 of them.

On the other hand Svalbard is a really nice subject for satellite imagery since it is very colorful – despite the arctic setting. There are areas with intense red color of the soil

other regions feature fairly lush green in summer like here near the capital Longyearbyen

while in the northeast there are some nearly bare areas of very bright limestone:

In addition to the color mosaic you can – as usual – also get a vegetation map showing the maximum amount of vegetation everywhere on the islands:

Check out the description and further samples on services.imagico.de and let me know if you are interested in this data set.

landsat_dach_veg_980

September 1, 2015
by chris
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Vegetation mapping

Supplemental to the Landsat mosaic of Germany and the Alps you can now also get a vegetation map generated from the same source data. Like the Green Marble vegetation map this shows the fraction of vegetation cover differentiated by vegetation type, but with a significantly higher resolution of 30 meters. The illustrations here show this rendered in two different green tones – a bright yellow green for the herbaceous vegetation and a darker green for the woody vegetation. Bright beige is used for the unvegetated areas.

Here an example from northern Italy around Milano:

And here another one from Switzerland in the upper Rhone valley:

As usual it is available on services.imagico.de for your applications – send me a message through the form there or via email if you are interested in this.

osmim_980

September 1, 2015
by chris
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New images for mapping in OSM

Two new images were added to the OSM images for mapping layer:

The former is from the Alaska Range which is currently quite popular since its highest mountain which is also the highest mountain in North America has recently been officially renamed to Denali. The image provides more up-to-date and largely better readable coverage of the area than the common imagery layers from Bing and Mapbox.

The latter is the Rann of Kutch i recently pointed out as the location where the coastline in OpenStreetMap contains the largest error. Although this area is well covered in Bing with high resolution images the shallow water and changing water levels make mapping based on these images very difficult. I put up a false color infrared image here from the beginning of the year, showing moderate water levels. During monsoon season much of this region is flooded and during the driest part of the year before the start of the monsoon it is even drier. Mapping based on this requires both familiarity with the area and some experience with reading false color infrared images. But based on such knowledge these images should significantly simplify proper mapping.

August 29, 2015
by chris
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Science and OpenStreetMap and why not call it ‘VGI’

These days OpenStreetMap is getting quite popular as a subject of study in social and geoinformation sciences. A lot of research papers are published on this matter and the term ‘VGI’ (volunteered geographic information) is a popular buzzword in this context, it seems to become almost a fixed requirement to use it in any scientific text dealing with OpenStreetMap in some form. Nearly always it is essentially used as a chiffre for OpenStreetMap – the idea being that by genericizing you make your results more universal. This almost never works since either you are only dealing with OpenStreetMap and not with any other alleged ‘VGI’ projects or you are putting OpenStreetMap in a box with other very different projects of crowd sourced data and are probably neglecting to properly analyze the differences.

On its own the term ‘VGI’ is a really bad choice due to several problems:

  • The key term is ‘volunteered’ which bears the question what it is meant to contrast with, i.e. what ‘non-volunteered geographic information’ is supposed to be. Also the question arises if and to what extent the data in OpenStreetMap can actually be considered volunteered more than data in other geographic databases. It if fairly unclear who volunteers what in case of OpenStreetMap – is data mapped by a paid mapper based on satellite imagery ‘volunteered information’? Is it volunteered by the mapper? By the satellite image provider? By the owner of the satellite?
  • The use of the term ‘information’ emphasizes these problems even further since it specifically refers to the underlying semantics of geographic data and not the concrete data representation.
  • For someone to actually substantially ‘volunteer information’ this would in fact have to be private, privileged – like when you map details of your backyard or inside your house only accessible to you. One of the core principles of OpenStreetMap is however verifiability – so information is either not really suited for OSM or it is not really volunteered since it is openly accessible to others as well so it is at most voluntarily entered by the mapper into the OSM database (although again the question would be how this could be non-voluntarily). So in a way this term is quite demeaning for OpenStreetMap since it does not acknowledge the principle of verifiability.

Although i am not sure if this played a role in coining this term ‘VGI’ underlines the idea that information is property and can and is usually owned by someone and that such information can only become free information by the owner volunteering it. This is actually diametrical to the core idea of the OpenStreetMap project to collect information in an open database that is inherently free because it is independently verifiable by anyone.

So if you want to use a catchy term something like ‘crowd sourced geodata’ might be more fitting but you’d better think well if it really is useful and necessary to use a genericized term in your case.

cl_date_512

August 24, 2015
by chris
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OSM Coastline and glacier data quality reports

Some might have noticed that in spring i skipped my usual report on the OpenStreetMap coastline data quality. I have now prepared a whole year update on that as well as a similar report on the glacier data (where my original report was from end 2013)

Short summary: Nothing big has happened with either coastlines or glaciers. There is steady progress though, which is nice to see especially in case of glaciers which is generally not a very popular subject. Here are the current node age maps for both – click on the images to read the full reports:

Not that much has changed about the worst parts of the OpenStreetMap coastline but there is some progress. Which inevitably leads me to the list of most serious errors of the coastline a.k.a. the best chances for membership in the zoom level zero club:

  1. The Rann of Kutch at the India/Pakistan border, see here which should not be coastline since it is only seasonally flooded (slightly changed but still more than 50km error)
  2. Northwest Ellesmere Island (more than 20km error)
  3. Eastern Greenland ice coast (about 20km error, glacier and coastline are not consistent in OSM here, Bing and many other satellite mosaics are not correct either)
  4. Various parts of eastern Sulawesi (~7km)
  5. Miller Island near Ellesmere Island in northern Canada (~6km)
  6. Southern Chile coast (moved down in the list due to improvements but still errors of several km)
  7. Southeast coast of Nordaustlandet, Svalbard (more than 5km due to glacier changes)
  8. Eastern Devon Island (20km error) fixed!
  9. Kirov Islands, Kara Sea in northern Russia (~10km) fixed!
  10. Seluan Island in Indonesia (~5km) fixed!
LC82141052015231LGN00_exp.ann

August 22, 2015
by chris
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Antarctic spring 2015

Here a recent Landsat image showing the return of the sun to the Antarctic after the southern hemisphere winter.

The location is near the tip of the Antarctic peninsula at Seymour Island with the eastern end of James Ross Island on the left and Snow Hill Island at the bottom.

The area is one of the driest parts of the Antarctic peninsula with Seymour Island being completely glacier-free. In the following crop of the island you can see the runway of the Argentine Marambio Base which was the first permanent airfield to be built in the Antarctic.

The following second crop shows the area between James Ross Island and Snow Hill Island. Well visible are the darker areas of snow free glacier ice. The snow cover accumulating during winter is very thin here. The sea ice in the middle of this crop is from this winter while the ice on the very left bottom is older, it did not break up during the last southern hemisphere summer. In this area coastal ice can sometimes get several years old before it dissolves during a particularly warm summer.

snub_980

August 21, 2015
by chris
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Some pattern math – regular patterns

There are now also various options to generate regular patterns in my pattern generator tool. The difficulty here is that from the map rendering side there is usually the constraint that the pattern has to be square with a size in pixel that equals a power of two. This makes it easily possible for map renderers to render it correctly tiled.

The problem is the most dense regular dot pattern where each point has six closest neighbors forming a hexagon (see above) does not have a square aspect ratio, it is sqrt(3)/2. So a most densely packed regular dot pattern cannot be rendered into a periodic square tile at any size. What you can do and what i did for the pattern generator tool is slightly stretch this grid so it fits into a square tiling. Depending on the size of the pattern compared to the size of the grid the required mismatch varies.

A square grid is of course no problem to fit into a square tile but its density and symmetry are often not what works best. There are other options though – the most interesting one is probably the snub square pattern which fits into a square tile at any scale. Its density is lower than of the triangular pattern where each point has six nearest neighbors but higher than of the square pattern with only four nearest neighbors. Based on the five nearest neightbors it is symbolized by the number ’5′ in the jsdotpattern interface.

This pattern also does not have such an obvious long range symmetry as the other regular patterns meaning it looks more like the relaxed random patterns.

It can also produce some pretty cool results with some of the regularly shaped symbols:

All pattern images above are linked to the corresponding settings in jsdotpattern. In addition to these features i also added the possibility to set colors for the preview for background and symbols. Try it out or get the code.

nz_sat_980

August 19, 2015
by chris
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Novaya Zemlya map

After producing the Franz Josef Land map and the Severnaya Zemlya map i have now completed another similar map of the third large group of islands in the Russian Arctic: Novaya Zemlya.

Novaya Zemlya is located south of Franz Josef Land and north of the Ural mountains at the eastern edge of Europe. It is best known as the main former nuclear test site of the Soviet Union. It consists of two large islands, Severny and Yuzhny Island which are separated by a narrow fjord, the Matochkin Strait. The northern island contains the largest glacier of Europe, the Severny Island ice cap.

Novaya Zemlya was the first island in the high Arctic to be discovered by explorers from western Europe. Willem Barents first landed there 1595. The islands separate the Barents Sea from the Kara Sea with a relatively sharp contrast: while the west coast is largely ice free even for most of the winter ice often persists at the east coast quite late into the summer.

The map employs the dot pattern rendering i introduced some time ago on a larger scale and generally improves on the mapping and map rendering techniques.

The satellite image mosaic is almost fully generated from Landsat 8 data from the last three years.

You can browse the map on maps.imagico.de and find the map data and imagery for licensing on services.imagico.de.

August 19, 2015
by chris
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Elevation data search now with complete SRTM 1 second data

Recently the USGS released the last part of the SRTM i second data set. I updated the elevation data search tool to include that – you can now find all 1 arc second tiles available there, just check Global SRTM 1″ in global sources, mark your area of interest and hit search – you will get a link list with all files you can download via USGS Earthexplorer after logging in there.

If you need custom processings of this data like for example with waterbody flattening or seamless merging with other data sources – i provide such services, just drop me a note.