Sensor Web, Geoprocessing, Security & GeoRM, Geostatistics, Semantics, 3D, Ilwis, Earth Observation

ILWIS and 3D

September 26th, 2011 @ 11:04 by Martin Schouwenburg
Posted in 3D, 52°North, ILWIS

In the past ILWIS had limited 3D capabilities. One could make a GeoRef3D which generated a 3D image (with a DTM) but it was cumbersome to use and quite slow. One of the goals of the 3.8 was upgrading these capabilities to something usefull.
In line with the design goals as mentioned in a previous blog, the idea was to create a 3D enviroment that could be helpfull for visual analysis. When one looks at a rendering of a map (2D), basically you explore the relations between the spatial locations and one or more attributes that are related to that spatial location. The most used is of course some color representing the value of an attribute. There are several schemes to enhance this ( number of attributea) in 2D but they often become a bit confusing.
If we use 3D space we can visualize the relation between spatial (X, Y) and two attributes in a simple way. We simply map the Z dimension onto a numerical attribute and still use different color ( or other form of representation) for the other attribute. This was for me the corner stone when designing 3D. So for example, the picture below shows the NDVI for a certain period (color) and the average precipitation (Z dimension) of the same period for the southern half of Africa.

So, how do we do those things? If you look at the Layer view at the left, you may notice two things that are different from the regular situation. First of all, in “global tools”, the 3D mark is checked. If checked the whole view shifts to 3D mode. But as the view has no default Z information, its just a flat map viewed in 3D. To add the Z information we activate the 3D properties tool ( context menu, right mouse button, on “Display tools”). Now we have a new tool in the tree, 3D Properties. To add a “real” Z value, double click on “Data Source”.  We get now a small form with a few options

  • Self. This means the Z information comes from the values of the map it self. Usefull for DTM’s and such
  • Rastermap. Select another value rastermap of the same geographic area. The values of identical coordinates on the source map will be used as Z information on the 3D view.
  • Maplist, only relevant for 3D animations. Every map in the animation is linked to a map in the maplist
  • Attribute column. The Z information comes from an attribute column of the map.
Double clicking on the “Scaling” node will open the scaling form with which you can change the scaling and offset of the Z information.
Moving through 3D space happens with the mouse buttons and mouse wheel while the ctrl key is pressed.  With the left button you rotate around the map, the mouse wheeel changes the distance to the map and the right button changes the point which you are looking at. It is possible that this movement model will change slightly as I am not 100% satisfied with it.
These are the basics of 3D in ILWIS 3.8. One can also combine 3D in several layers. The picture below comes from a combination of a DTM layer and precipitation layer.
Actually it comes from an animation where rain clouds move over a portion of Ethiopia.
 Three D has some limitations with respect to memory. At the moment the size of the rastermaps poses limitations. Beyond a certain size you might get out-of-memory errors and the visualization will not work.
3D isnt limited to raster maps, also vector maps can be used in 3D. Usualy, the Z information comes then from a attribute table but the other datasources are also possible. Below as picture of 2 segment layers that use the Z information of a DTM for the Z information. The contour maps also has extrusion on to better visualize its position in 3D space.
3D will be further developed in ILWIS with new tools ( e.g. space-time cube) but that is for after 3.8.

The new Layer view of the Map window

September 19th, 2011 @ 08:44 by Martin Schouwenburg
Posted in ILWIS

As people may have noticed who looked at the beta-1 of ILWIS 3.8, the way the user interacts with the layers displayed in the Map window is significantly different from previous versions. Basically the windows menu has been deprecated in favor of the layer view on the left side of the window. Almost all actions that changed the content of the rendering area are done through the layer view.

The reasoning behind this is a bit similar to why Microsoft invented the Ribbons. Menu items are to short lived. Menu items appear and disappear with the opening and closing of the menu. Even tasks that you do often need multiple clicks. Furthermore it is sometimes difficult to keep an overview where the different choices are “hidden”.

Ribbons ( basically expanded button bars), are an attempt to solve this, but I don’t like Ribbons. All the choices of the “old” menus suddenly stare me in the face, 80% of which I don’t need at the moment. The layer view is a middle ground between the “stare in your face” method of the Ribbons and the “Hide all” method of the old menus. Basically you can expand to the property you want to control (e.g. transparency) and keep that available while the rest of the properties are in a collapsed state.

There are two additional things to know. First of all, each layer has an item display tools. All tools, tools are “things” that alter the properties of the display, are grouped underneath here. The display tools item has a right mouse menu with which you can show/hide the tools for this layer. Not all tools are visible by default

So here we see that tools like for example 3D properties and Track profile are not shown by default. Checking them will add them to the tools and ready for use. Unchecking them will again remove them.

Second. On many tools you can double-click. This usually opens a small form with which you can change the properties of that tool. For example when you double click on a transparency tool you get a form with a slider to dynamically change the transparency of that item which the tool controls.

I still have to make an indicator if an item is “double-clickable” or not.

In the Layer view there are two special “nodes”. Global tools and Background. As the name sugests, global tools are tools that influence the view of all layers in the map window. Background controls the special “background layer” (coloring, transparency). Though mostely you won’t thouch this, it is possible as it is just another layer in the view.

All the tools are plug-ins. This enables programmers to create new tools without having to alter ILWIS itself. For example, last week I created a tool to display Hovmoller diagrams of tracks on the map without touching the rest of ILWIS.

52°North Thin SWE Client @ FOSS4G

September 16th, 2011 @ 18:46 by Arne Bröring
Posted in Sensor Web

Being at the FOSS4G conference in Denver, I just hold a presentation about our Thin SWE Client for the OGC Sensor Observation Service. The functionality of the client is focused on the display of time series data. This comprises a diagram view with comfortable navigation mechanisms (e.g. an overview time series, panning, zooming, etc.). In addition a table view showing all measured values belonging to a selected time series, as well as a map overview for displaying the sensor locations are included. This display functionality is complemented by further features like an export function (CSV, XLS and PDF export) and comfortable menus that help users to select the data they are interested in.

Besides giving the presentation (please find it below), I demonstrated the software successfully 🙂 If you are keen to see the application in action yourself, please visit our demo deployment.

The Why? of ILWIS 3.8

September 12th, 2011 @ 11:17 by Martin Schouwenburg
Posted in ILWIS

My first few blogs will be about the upcomming 3.8 of which I published a first beta just before my holidays. The next beta will follow shortly.

The last few years, as a programmer, I encountered serious limitations in what ILWIS could render on the screen. The rendering system was designed when computers had far less memomry, puny (compared to now) graphic processors and the data-sets were much smaller. With large, multi-spectral and spatial – temporal data-sets, with big feature sets, web technology etc.., the existing system ran into serious limitations.

After some discussion and brain storming I designed a new system that had the following goals

– Flexibility.
I didnt want to have to change the internals of ILWIS when implementing a new type of rendering. For example if I want to add a renderer for a WFS service, I only have to write a plug-in for that kind of data stream, I don’t have to touch the rest of ILWIS which simplifies design (and debugging 🙂 )

– Rastermaps with different geometries in the same mapwindow.
“Old” ILWIS was limited, only rastermaps with the same georeference are allowed in a mapwindow. With the current graphics processors this is no longer needed. They are able to morph bitmaps (and in the end, renderings of maps are just bitmaps) on the fly. So as long as you supply the correct parameters, instantaneous resampling is done for you. This also means that maps are now oriented along the coordinate system instead along the georeference.

– 3D.
People like 3D, even if I may have some reservations about 3D rendering for spatial data, people seem to like it and find it usefull. So this was also one of the goals. The option to view all spatial data in 3D. But my goals went a little bit beyond that, as (see below) one of my additional goals was visual spatial analysis, I wanted to go further then simple 3D renderings of DTM’s and such. The “z” axis had to be a arbitrary numerical value of any data-source as long I could relate the spatial x,y coordinates to that datasource. So an attribute table, a different rastermap, the maps it self etcetera, are all suitable. Now you can make 3D renderings of temperature maps, DTM’s, NDVI’s, population density, the sky is the limit. Which combination is usefull and which not is up to the user, the system poses no limits here.

-Animations.
The “old” ILwis had a primitive animation component which was not that usefull. These days, with big spatial temporal data-sets that are difficult to visualy analyze without some type animation, ILWIS was not the best tool for that.
My goal was to have an animation layer that worked in every way (were relevant) as a normal layer in the mapwindow. The only difference was that what it displayed changed over time (animation!, tadaa). Animation had to work both on “real-time” information(if available, a subject for a different blog maybe, as ILWIS now knows about time) or on a simple index basis. Also synchronization between different animations had to be realized. Apart from that, were relevant, all tools that worked on “normal maps” also had to work on animations. So for example, 3D animations are possible.

– Visual analyses.
The over-arching goal behind this is “visual-analysis”. Though algorithmical analysis is needed to produce the hard numbers needed for scientific work it is sometimes difficult to spot were your analysis should start. Nature has gifted us with a wonderfull tool to spot patterns and trends in the shape of our vision. So making tools that enhance that capability makes perfect sense. This is what I call visual analysis. I added a lot of display tools to the new rendering to help the user in this respect. Interactive representation, real-time stretching, transparencies, 3D tools, animations etcetera are an expression of this. The goal is not to make prety pictures, scene rendering software is better for this, but to make visualy meaningfull images(which might be pretty 🙂 ).

52°North Summer Party

September 5th, 2011 @ 14:50 by Ann Hitchcock
Posted in 52°North, Communities

52°North staff members took a few hours to relax and enjoy the summer rays at their “Sommerfest” last week.Life is not always all work and no play!

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