Month: May 2018

Generally, all layers of geographic data have the description of the coordinates system. Unfortunately, this is not always the case. Usually, this problem increases by not being able to contact the creator of the data.

Diagnosis of the problem

A- You ask QGis to load a vector layer and you see a window displayed that reads “Reference Coordinates System Selector “. If it’s a layer with a “shape” format, the data must not have a defined coordinates system. In the case of shapefiles, the PRJ file is missing.

B- You ask QGis to load the layer and, without any window opening, you do not see your new data, or they elsewhere from where they should be.
Before believing that there is, actually, a problem with your data, make sure that you have checked the Projection in ”   Project Properties   »->«   SCR   “.
If the box is checked, the data has a defined coordinates system, but it is false. The PRJ file exists, but its contents is wrong. Continue reading “How to find the coordinates system of a layer in QGis?”

If you’re trying out the new QGis 3 and you’re a fan of OpenStreetMap, most certainly you’ll wondering where are in this new version the plugins you used in the 2.18 version.

I you search in internet, you’ll come across many articles telling you that version 3 requires a redevelopment of plugins, that you must be patient and wait … Continue reading “QGis 3 (and QGis cloud) and OpenStreetMap”

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”

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 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”

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”

 

 

How to open a window with Street View and Bing Bird’s Eye using your QGis  Mapping ArcMap window? Easy, follow the guide … Continue reading “Google StreetView and Bing Bird’s Eye in ArcGis and QGis”

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”

 

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”

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)”