Welcome to the second part of the test of the Open-Source GIS tools mentioned by the http://gisgeography.com. In this test we took Top 4 tools from their list and we are trying to load our data and compose a simple map.
The first part you can find under this link:
In the previous part we managed to visit various software websites, download the tools, load the data in various formats: vector, raster and table/XYZ data. Now its time to edit the layers we’ve loaded in our open-source programs and finally make a real map. Although in this test are taking place all top 4 tools from the ranking Quantum GIS serves as reference tool for other three. I know it the best so it might be not fair to compare it with the software used for the first time.
Now when we have our data loaded let’s edit the features on our map a little.
Editing the vector layer
In QGIS by right-clicking the layer in your layers tree you can access the layer’s properties. It is powerful tool where you can edit styles (colour, pattern, border, line thickness, labels and many more) of the vector layers. As QGIS is our reference tool I will try to make all the other maps looks similar to made in Quantum GIS.
Point vector layers will be red and blue with labels attached (‘Name’ attribute as label for CSV file and ‘Well ID’ as attribute for wells layer). Seismic lines will be brown and we will add some more thickness to make them visible better.
Editing polygons is more complicated as you can fill the polygon with pattern and also edit boundary line. In this case we have two layers of protected areas. One will be blue and other green. Both filled with diagonal lines.
gVSIG also gives you opportunity to edit layers quite easy. Right click on the layer in layers tree opens menu from which you can access layer properties. gVSIG offers you tools to edit your layer style in also very wide range similar to QGIS. We can edit shape, colour it and also pick the labels for the desired layer.
As we want to keep our maps similar we have to edit the polygons. We can pick the polygon fill from the library or create it by ourselves. There are quite a lot options in gVSIG which we can change in our layers style.
Whitebox GAT similarly to QGIS and gVSIG offers some editing options after right click of the selected layer in the layers menu. We can edit easily point and line vector layer choosing color and point/line size. Unfortunately I couldn’t find anywhere an option of adding labels to the point layers.
Polygons can be edited in similar manner. To be honest with you there are not too many editing options (or I couldn’t find them). You are not able to set up transparency or edit the polygon fill. I had to set up only polygon colour which does not satisfy me at all as it covers the content under the polygon layer.
Editing layers in SAGA is totally different from the previously tested tools. When you select your layer in the Map menu, layer properties menu appears right away in the window between menu and main map view (workspace). There are couple of options which you can use to edit your layer style and its labeling. You just have to remember to press Apply after every change. Otherwise changes will not be applied to the layer.
Editing the polygons has exactly the same path. Your properties menu will give you all the tools necessary to edit the polygon layer. It gives less options than QGIS and gVSIG however it is absolutely enough to make good layers style editing for your simple map.
Editing the raster layer
Our basemap is a georeferenced raster which acctually does not need too much editing. The only thing which we would like to do is removing black boundary which was caused somehow by rotating the raster during georeferencing process. (see: How to georeference scanned image in QGIS and vectorize items from OpenStreetMap-part 1.) We are talking here only about cosmetic change.
In Quantum GIS you can access raster layer properties by right-clicking this layer in the layers menu. In the properties menu you are able to select which colours on the raster should be transparent. This is the trick how to get rid of the black margin around your raster. Just set the black colour transparent.
gVSIG also offers you very nice tool to remove black margins from your rasters. In raster properties you will find very similar way of doing this as in QGIS. Just select which colour you would like to make transparent.
In Whitebox GAT we had problem with our raster display after import. Also there is no menu to switch the raster layer properties. Unfortunately we have to skip Whitebox GAT at this stage.
SAGA raster was imported without the black boundary around however from the beginning the imported base map does not look as it should. However there are some editing options in SAGA such as transparency – in our case not selective. You can make transparent whole raster not only the chosen colours. We will skip SAGA here as well.
Simple data interpolation
To make our task more complex let’s interpolate Elevations which are given in wells layer attributes. Then we will make isolines using these data.
In Quantum GIS we have to interpolate in two steps. First is to create raster. After that based on this raster we are able to create isolines. To do so you will need to download interpolation addon available in plugins repository (see slideshow).
First we have to choose the layer with the elevation data. That would be the wells layer. Then we need to set up interpolation method and parameters. Let’s put here anything and interploate with Inverse Distance Method. Also we need to specify where the raster layer needs to be stored. After completing the interpolation we should see the raster surface. Note that the value of colur (grid node) is the value of interpolated elevation.
We will have to extract isolines from this raster using contour tool from the Raster Menu/Extraction. We need to set up intervals (in our case 10 meters) and select folder for storing our isolines. Those will be extracted as a shapefile (shp).
After completing this part let’s turn off the raster layer, we won’t need it anymore. Then as a last step let’s just edit the layer as simple vector layer changing the color, labeling and thickness.
Interpolating data in gVSIG turned out to be not very straightforward. I had to search for hints how to do it. This is what I’ve found.
First we need to Rasterize our data with proper plugin from the Toolbox. After setting proper parameters (see the images) our data were rasterized – you can notice small black dots present coles to your wells (red points). Then we need to use function called Void Filling – I assume it fills the gaps in our raster. After running this tool we obtain raster surface similar to what we got in QGIS. Then we have to use plugin called Contour lines. After using it we see contour lines made basing on our raster/grid. We just need to edit the contour lines and remove or turn off the raster surface from the layers tree. Effect is very good however it is not very intuitive process.
In Whitebox GAT we need to look for interpolation tool in the toolbox. There are couple of methods to select and generally this toolbox is really nice and has many tools. Let’s pick IDW (inverse distance) interpolation. All the tools have wide description and even script visible for everyone who would like to see exactly how the tool works. After setting up some parameters we obtain intepolated surface. Then we need to use one more tool from the toolbox called Contour. It is also easy to use – description tells everything in case of any doubts. After running the tool we should see contour which is quite sharp and not looking very nice. In the Contour description there was suggestion to use another tool called Smooth. Let’s find this tool in the search tool available in bottom left part of the screen. It really helps to find stuff in the toolbox. After running of our Smooth tool isolines look much better. Now let’s edit the style, unfortunately no labeling available. That was quite nice and easy.
SAGA GIS also has a large Toolbox and we are going to use it. Let’s look for some interpolation tools. We will use Grid – Inverse Distance method. All the parameters and source we can set up in the new menu which appeared between Toolbox and main map view. After running the tool we see new layer which is colorful elevation grid. Now we want to extract contours from it. I couldn’t find proper tool in the Toolbox but SAGA has very nice feature. You can search for the term (for example Contour) that you need using the Find and Run Tool (see images). I see that there are two tools available Contour Lines from Grid and Contour Lines from Points! We will test both. We can make our map as we did in previously tested programs. Using Contour from Grid tool w can easily extract contours. Another option is even better. We can make interpolation quickly without creating new raster layer. This is the quickest method so far. Now after using of both methods you can see two sets of contours on the slides. Let’s pick one and edit the style in the layer menu and turn off the visibility of the interpolated elevations grid. We can also add labels to our isolines. Interpolating in SAGA is great, only the color scale is very poor and the colors are weird in my opinion (contours should be Orange and for me it is more brown).
Our map is ready. The last thing which left to do is composing a map and exporting it.
Quantum GIS uses Print Composer tool where you can adjust your map area for printing, set up scale, add items like legend or the scale bar. You just need to prepare your map for printing/exporting using menus visible on the sides. Those are quite straightforward and offer you lots of options to change. You can export map as JPG or PDF.
gVSIG offers very similar tool. You can find it in Project Manager and it is called the Map. Separate window opens where you have to choose from the list your View – which was your workspace. There you can easily modify the map adding labels and scale bar. It seems to have less options than QGIS but it also works very well.
In Whitebox GAT map composing concept is little different. Your workspace is also your map which you want to export. There is no additional tool such as Map Composer. Additional menu, called Cartographic, allows you to add labels, scalebar and legend. There are not too many options of edition but it is quite good and intuitive for simple map making.
SAGA presents similar concept to Whitebox GAT. I couldn’t find any additional map composer so it seems that the workspace is acctually your map. You can add scale bar and north arrow directly to it. There is also something like Print Layout which additonally shows the legend on the side and this is probably the place where you can print your map together with legend. However after saving your workspace as image your map is succesfully exported but with legend in separate file. It would be nice if there would be option to save the map to a file together with the legend not separately:)
This is the end of the test of the Top 4 Open-Source GIS tools from http://www.gisgeography.com list. I hope you liked it although it was quite long.
Few words about the tested tools:
Quantum GIS (QGIS)
It was reference software for this test so it shouldn’t be classified in this competition. In my opinion it is the best Open-Source GIS tool available now for FREE. Even in basic version it has many many options and you can find even more extending its functionality using plugins, additional toolbox or even writing your own addons. It works with many file formats and I always used it as cross-communication tool between other professional products like geological and seismic workstations or simple Microsoft Office datasets. I’ve been working couple of years on this software and I see that many bugs were fixed and now it is really reliable tool where you can make quality analyses and mapping.
Its been a while (couple of years) since I last used gVSIG and in the past it did not impress me too much. I completely forgot about it. Now I was positively surprised by its performance and funcionality. It is intuitive, it works with many file formats and it is possible to make nice analyses using its toolbox. It has interface to which I had to get used but maybe some people would prefer it more than classic approach used in QGIS.
It seems that this project is not as much developed as QGIS and gVSIG. It seems to be very simple tool, however it has functional toolbox where you can find lots of interesting analytic tools. It has limited editing options (few possibilities of vector layers editing) and I was not able to properly import raster layer (maybe it was my fault). There are many things which you can make really quick in this program but it gives you impression of lack of control on what you want to do. Also one dissapointing thing for me is no Coordinate System tab or menu. Lack of chance to edit or check the coordinate system is painful in GIS software.
SAGA interface on the first look seems to be not user friendly. If you want to pretend that you are smart scientist just put SAGA interface on the presentation. Everyone will think that you are doing important and incredibly difficult analysis. However after some time you will see that this interface is quite unique and it has lots of options and settings ready to use without searching for them in hidden tabs. It has totally different design of changing and applying options but also has lots of functions and tools. The only disadvantage is lack of real map composer which you would like to have to present results of your analysis nicely .
Summarizing I think I would generally agree with the list put on http://www.gisgeography.com with one exception. I would give SAGA place number 3 and Whitebox GAT number 4. I think that SAGA has more options of editing and analysing of your data and is more real GIS tool thanks to its Coordinate Systems database and CS options.
Oh! And here are the final maps made in those tools. (for Whitebox map I used Elevation grid instead of scan which was loaded badly). Pick your favourite!:)