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 (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:

ArcHydro: how to model the water resources of a territory: 1-Install

ArcHydro Presentation

ArcHydro is a set of data models and tools that work under ARCGis to support the data analysis of superficial water resources.

You can use ArcHydro to delineate and characterize the watershed lines, define and analyze the hydrogeometric network, manage the chronological data and export data to digital models. Continue reading “ArcHydro: how to model the water resources of a territory: 1-Install”

Make a  topographic map with QGis

Thanks to the SRTM project we can access to a comprehensive world coverage of land elevation data. It has become very simple to create one’s own  topographic maps with QGis .

We will discuss here :

  • – how to download  elevation data for the area of interest
  • – how to format the display style to fit the standards of the topographic maps
  • – how to enhance the viewing using a “shady” layer type
  • – and finally how to generate contours Continue reading “Make a  topographic map with QGis”

The spatial-temporal cube of ArcGis : 2- Hot and Cold Spots

In the previous article (Le Cube spatio-temporel d’ArcGis : 1- découverte) we discussed how to create a spatial-temporal cube from a cloud of XYZ points.

  The points are grouped into ” boxes ” (bins) corresponding to 3D pixels.
We have discussed how to depict them in an ArcGis Pro 3D scene. In this article we will discuss how to analyze the temporal trends of the bins values, using the analysis of emerging hot spots. Continue reading “The spatial-temporal cube of ArcGis : 2- Hot and Cold Spots”

The spatial-temporal cube of ArcGis : 1- discovery

One of the domains of GIS where still remains a lot to be done is the field of temporal analysis  . While almost all the available tools focus on the spatial evolution of a phenomenon, we are left helpless when trying to visualize or analyse a phenomenon that changes as a function of time as well.

For some time, we have the support of animation tools that allow us to see a sequence of maps and perceive the change over time. Regardless of how useful they are for communication, they are useless to perform a serious data analysis. In this series of articles, we will discuss new  ArcMap and ArcGis Pro tools available  in the form of a Toolkit Tools model for the  spatial-temporal exploration (Time Pattern Mining). An example has been selected in order to process, at first with ArcGis Pro, and, later, with ArcMap. Continue reading “The spatial-temporal cube of ArcGis : 1- discovery”