EqDistant Plugin How-To and guides

Welcome to EqDistant Plugin website!

EqDistant Plugin is a QGIS plugin to create an equidistance line. Equidistance line is a line which every point of the line is equidistant from the nearest points on input lines. Equidistance line is often used to determine maritime boundary between two states, where the input are the baselines of the bordering states.

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Equidistance construction algorithm used by this plugin is based on steps of constructing equidistance line in Technical Aspects on the Law of the Sea (TALOS). Based on the geometry of the bordering baseline, there are two types of equidistance line. The first one is created from adjacent state, where the coasts of each state are adjacent to each other. The other one is opposite state equidistance line, where the coasts of each states are opposite to each other. The contstruction algorithm between these two types of equdistance line is slightly different, so you may want to keep in mind these types while creating the equidistance line.

Watch Me!

If you want to see EqDistant Plugin in action, just click these videos below.

Are You Ready?

If you see this page, you might already install the plugin in your QGIS. Right?. But if you somehow haven't install it yet, here's someway to install the plugin into your QGIS from the repository.

This plugin requires a QGIS version 2.0 or higher to run. Before opening QGIS, make sure your computer is connected to the internet.
Repository is an online storage where the plugin is stored. To add EqDistant plugin to your QGIS installation, open Plugins > Manage and Installs Plugins .... In the next dialog, Click All tab. There you should find the EqDistant plugin which is stored in QGIS repostory ready to be installed.
However, if somehow you can't find it, you need to install the plugin from another repository. Go to Settings tab and click Add... button to add custom repository. Specify any name you want in the name section, but you have to fill http://ivanbusthomi.github.io/repository/plugins.xml as URL.
Now that EqDistant plugin is listed in your plugin list, you can start installing the plugin by clicking Install button.

Yeah! Let's Start

The first thing to keep in mind is this plugin uses line layers as input. So, if your layer data is stored in polygon geometry type you might need to convert that to line layers. You can do this using Polygon to Line tools in Vector > Geometry Tools > Polygons to Line. After converting your layer geometry type, edit the data by deleting unused line segment within the layer. This will decrease the time needed in processing your data.


If you already have the line layer, make sure that the Coordinate Reference System (CRS) of your layer is UTM, or any CRS using meter as unit. If your layer still in geographic coordinate (the unit is in degrees), you need to reproject the layer to UTM or another CRS as long as the unit is in meter. Make sure you have the right CRS by looking into your layer's metadata in Layer Properties dialog under Metadata tab.


When you have those two conditions above met, then you are good to go! Now, go ahead and click the icon of EqDistant plugin, and you will see the main dialog of the plugin like below. Keep in mind that you have to load atleast two line layers in order for the dialog to shows. Grab the sample data Here!.


So, What Do You Want to Get?


By default, without checking anything in Additional Result section you will always get an equidistance line as result. Other than that, you can get the equidistance points which is basically list of point which construct the equidistance line. If you want to know the coordinate of every point in the line, you might want to check this result type.

Another result type you can get is the construction line. By checking this option, you will be able to know which points in the baseline layer is used as input in creating the equidistance line. This is also usefull as a tool to check whether your result is right or not. In some cases you might meet some funny result where some line just crossing each other or, you know, some weird stuff happen. If you have construction line information, you can always know which segments or points need to be edited. (yeah unfortunately, the result from this plugin sometimes need to be edited to get those nice clean looking equidistance line. No worry, i'm still working on it)

Pick Starting Point

Remember about the types of equidistance line in boundary making mentioned above? If you don't you might want to scroll up again. In this step we'll choose which equidistance line type we should choose. If your baseline layer is opposite to each other, then you have to choose the opposite case. If your baseline layer is adjacent to each other, which means there is a point where the two baselines meet, then you have to choose the adjacent case. You can choose wether it is an opposite case or adjacent case by switching the tab shown in the picture below.

You will notice that the following option after switching the tab also change. In the Opposite case, you will need to specify four points, two in each segment. This two points are the starting and ending point of the segment in which the equidistance line will be created. In the other hand, adjacent case only need two input points, one in each segment which is the starting point. the ending point is defined where the two segments meet or intersect.

Defining the input point is pretty simple. You can do this by clicking the button and click on the map near your starting or ending point for each segment. After clicking the map, then in the box near the button you will see the coordinate of the point you just clicked.

If you have all those box filled then you are good to go ... to the next step, ofcourse.

Last Setting!

Interval distance is the searching distance to find the next point in the algorithm. The shorter the distance you define, the result point you get will likely (but not always) closer to each other. The line segment will also has more vertices in it, which will result smoother (but not always better) equidistance line. The time needed in order to process the whole data will also be longer. The setting goes vice versa if you input longer interval distance. So it will be best to try different interval distance which will result best equidistance line for your case.

Saving Your Result

The result you get from the plugin is saved by default in a temporary layer. So, if you already get the best result, you have to manually save it to your diskdrive using QGIS layer saving feature. You can do this by rightclicking the layer you want to save and click Save Layer As. The next part is pretty much self-explanatory, i hope. :)

Congratulations!

Now that you have your equidistance line, you can simulate your boundary line using equidistance method. Note that the result you get will sometimes contains bugs or inperfect. Therefore, you have to manually recheck your result by looking at the geometry of your line result. Construction line also will help alot during recheck process since the lines should not be crossing one another. If there are construction lines that cross each other, most likely that part is still imperfect.

For more information and feedback, send me email at ivanbusthomi@gmail.com. Cheers!