Processing algorithms in the QGis 2.8 Graphic Modeler

Adding Algorithms in the Graphic Modeler

The algorithms are added in   the graphical modeler in the same way as the input data. You simply select the tab   algorithms   instead of the tab   Inputs, to see the display corresponding to the panel   Toolbox of treatments . Continue reading “Processing algorithms in the QGis 2.8 Graphic Modeler”

How to create terrain profiles in ArcGis or QGis

For those who are working with Digital Terrain Models, the topographic profiles (or field profiles) are a basic tool, either in the validation or in the processing phase. They make it possible to visualize the relief as a function of the route in a graph where the horizontal axe refers to the distance and vertical axe, the altitude.

Even if there are many specific software, here we will only see the two main GIS software: ArcGis and QGis.
For both examples, we will assume that you have a DTM displayed in the map window. Continue reading “How to create terrain profiles in ArcGis or QGis”

Geocoding Addresses with 2.8 QGis

Geocoding addresses allows you to transform addresses into a layer of points, from a text info into a spatial info. This is, mainly, used in geomarketing and transport, but due to the development of web applications it proves very useful in almost all areas of GIS.

The problem with geocoding is not technical but related to the evolution of techniques and available resources. If you search on Google « géocodage adresses France » you will get some very detailed tutorials, but often out of date. Here is such a tutorial to the taste of the month of May 2015 that we will update (promised!) when he becomes obsolete. Continue reading “Geocoding Addresses with 2.8 QGis”

ArcGis and Python: before starting

Getting started with Python in ArcGIS is easier than it looks. There is no need to master Python in order to use it in a basic way in our work with ArcGIS.
First of all, there are several options for executing our processes with Python code. So we will start by discussing the different options and how to make the right choice for our needs, whether it is simply testing a code line or a piece of script or the complete execution of a script.

The difference between running a code line and executing a script, in terms of programming, is that for the first time we will use an   INTERPRETER   and secondly, we will use an   EDITOR. Continue reading “ArcGis and Python: before starting”

QGis and WEB: an update

The WEB is no longer reserved for large accounts. The technical means and the costs of the solutions are no longer an obstacle for everyone to publish on the WEB their data and maps.  But this development has gone hand in hand with a multiplication of technical solutions and the main obstacle, today, is to choose the best solution to one’s needs. We will discuss here a rather general overview, but which, I hope, will help you to make a suitable choice. Continue reading “QGis and WEB: an update”

Updated 28/04/2017Migrate postgresql databases with PgAdmin4: problems and solutions

 

The problem discussed in this article has been solved by the pgAdmin team (tested on the pgAdmin 1.4). If you come across this problem and you have a pgAdmin version older than version 4, just download and install the latest version). Nevertheless this method can, always, be used to circumvent possible pgAdmin error by re-using the syntax recovered on the error window. Continue reading “Updated 28/04/2017Migrate postgresql databases with PgAdmin4: problems and solutions”

Accuracy, uncertainty and linear alteration of geographic data (2)

In  the  previous article   we discussed the different geographic coordinate systems: astronomical, geocentric and geodetic coordinates. Let’s have a look at the possible sources of error. Continue reading “Accuracy, uncertainty and linear alteration of geographic data (2)”

Accuracy, uncertainty and linear alteration of geographic data (1)

It is not easy, in geomatics, to get a good grasp of the geodesy notions that underlie the manipulation of geographic data. Unfortunately, many users do not have a sound knowledge of these concepts. I have to admit, that this knowledge can become superfluous if, for example, all your data is in the same coordinate system. Continue reading “Accuracy, uncertainty and linear alteration of geographic data (1)”

ArcHydro: determination of the watersheds of a territory (2)

In the previous article, ArcHydro: determination of the watersheds of a territory (1), we analysed points 1, 2, and 3. In this article, we will discussed the last three points: