How to integrate DWG data in QGis

The DWG format is an Autocad proprietary binary format. When we want to load layers in QGis from this format, multiple problems arise.

QGis uses the GDAL library to read / write external formats , such as DWG.

Firstly a clarification: do not confuse the DWG format and DXF format. Often references for DWG / DXF format are found which is a misuse of language. Both formats are different . The DWG format is the native format for Autocad software. It is a proprietary format and, in theory, subject to license. The DXF format is a data export format for Autocad software. It is public and not subject to license.

Continue reading “How to integrate DWG data in QGis”

ArcBruTile new version, ArcGis 10.3 compatible

The ArcBruTile  0.5 new version is available. To download, follow this link: https://arcbrutile.codeplex.com/#


As it is not easy to have an updated documentation of this tool, in this article there is some useful information to make the most of it.

We will discuss one by one the toolbar available options.
OpenStreetMap

The available option under this menu item is Mapnik
Mapnik is a free map rendering software that is used by OSM to draw the main map. OSM uses Mapnik to draw 256 x 256 px squares, which are then delivered from the tile server at tile.openstreetmap.org.
Mapnik tiles are generated and stored on the tile.openstreetmap.org server. They are calculated by a weekly extraction which is currently carried out on Wednesday mornings (GMT / BST time zone). Each tile has its date of creation and a simple marking of obsolescence (flag or flag) meaning that it is ready to be recalculated. The rendering engine follows these few rules:

  • When a user checks a tile on the OSM site, there is an automatic control to discover if it is more than seven days older than.
  • If it is > seven days, it is ticked as obsolete (and , therefore, it will renew ).

A rendering process generates through a background process,  a list of all the ‘obsolete’ tiles and; then launches the new rendering for these tiles . Once finished , it requests for a new list of tiles marked as obsolete .

Therefore , if no one is watching an area, it will not be updated often . The tiles are recalculated according to interest / attention. To tick a tile as obsolete does not include those tiles  covering the same area at higher zoom levels as obsolete . If you read  ‘More OpenStreetMap coming soon …’ on a tile, it means that there is no data for this one and that it is on queue to be recalculated .

The other OSM rendering engine, Osmarender , is not accessible with ArcBruTile .

Bing

Since ArcBruTile no longer displays Google Maps , this option remains the most used . No need to search for Bing Traffic options , you are limited to basic displays .

Stamen

Stamen is a company based in San Francisco, that has developed applications from OpenStreetMaps .

The Terrain option only covers the United States, while two others , Watercolor and Toner, cover the whole world .

The option Watercolor is used for the map background. It applies effects on the OpenStreetMaps coverage that gives the map a hand drawing watercolor style.

The Toner option is a rendering black and white high contrast OpenStreetMap data.

The following figure shows an example of both options jointly .

Continue reading “ArcBruTile new version, ArcGis 10.3 compatible”

How to manage the South Italy projection with ArcGis and QGis.

The reference website for coordinate systems used during World War II is Thierry Arsicaud’s website : Notes on the “Modified British System” used on the European Theatre of Operations during the WWII.
In 1919, Great Britain adopted in its territory the “British System”, based on a Cassini-type map projection and the use of a grid designed to facilitate the reading of the coordinates of the designated points . This system was replaced in 1927 by the “ British Modified System”, more suited to cover large geographical areas and military operational use by land  or airlift forces.
This “British Modified” system was used during the second world war by the British and American armies by being extended to European, North African, the Near East and South East Asian operation theatres. The following figure , from Thierry Arsicaud’s website shows the areas corresponding to the projections in course during World War II.   

Continue reading “How to manage the South Italy projection with ArcGis and QGis.”

The War North projection, how to manage it with ArcGis.

Origin of the War North projection

Here is an excerpt of the thesis defended in November 2005 by Nicolas Guilhot, currently Lecturer in History and Management at IFROSS – University Lyon 3, at the Graduate School of Social and Law Sciences of LYON II University – LUMIERE. Those wishing to consult the full text will refer to: http://theses.univ-lyon2.fr/documents/lyon2/2005/guilhot_n
“As in many other areas of official cartography, the first world war confirmed and accentuated the current evolution in the projection systems used, and, even, if the preference for the quality of conformity was not questioned, a projection system more suitable to the new military needs was adopted: the war of position and the central role of artillery fire according to maps had demonstrated the need for the military to have, not only, geographical coordinates (degrees or grades), but also rectangular (kilometric) in order to obtain the coordinates of a position directly by their measurement on the map. However the polycentric system did not allow assembling several sheets in a coherent system of rectangular coordinates, a gap particularly problematic given the small area covered by the breaks in the master plans. During the war, the SGA had adopted Lambert’s projection in 1915, a consistent modified conic projection.

Continue reading “The War North projection, how to manage it with ArcGis.”

Tutorial: How to create an aptitude map with ArcMap, with and without fuzzy criteria (4)

So far we have dealt, simultaneously, with both methods of data processing corresponding to the different criteria for classifying the plots according to their ability to host a new school.

Both methods have resulted in some differences, but it is true that with a little effort, the classical method could be improved and, therefore, we could get equivalent results.

Now, we will attack the final phase, the aggregations of the four criteria, and there we will face much more significant differences.

Continue reading “Tutorial: How to create an aptitude map with ArcMap, with and without fuzzy criteria (4)”

ArcGis 10.3: apply a license to your geodatabase? ludicrous !

With version 10.3, ESRI has announced a new possibility for the geodatabase file: you can make them non-copy and you can give them a deadline access date. Firstly, let’s discuss all you have to do, then a nice example of how to make yourself absurd by living in isolation.

Firstly, let’s consider the ESRI terms in the descriptive page of this new feature :

Continue reading “ArcGis 10.3: apply a license to your geodatabase? ludicrous !”

ArcGis: Multiple attribute (1-n) spatial join

Joins between tables or layers pose virtually no problem when we have a unique match between the two elements we are trying to join. For one record of the reference table or layer, there is one or no record in the table or layer to be joined. The resulting table or layer of the join can be treated as any other table or layer.

Things always get complicated when the table or layer to be joined contains more than one record corresponding to the same reference record. This is called a 1-n relationship. We will discuss a hidden option that allows us to answer some of the questions we have in the event of 1-n type space joins. Firstly, let’s use a simple example.

Continue reading “ArcGis: Multiple attribute (1-n) spatial join”

ArcGis and Python (3 ): Your first script

If you have read the two previous articles   ArcGis and Python: Before your first steps and   ArcGis and Python: getting started , you are ready to get started.

There are two things you need to learn: the Python language and how to use the ArcGis Python geoprocessing library. As for Python, tutorials abound. But do not forget that you will only need some basics of the language. You will basically string together already existing ArcGis tools.

Continue reading “ArcGis and Python (3 ): Your first script”

ArcGis and Python (2 ): for a good start

Have you decided to get started? It’s time to put all the assets on your side . It’s already enough complicated to learn a new language, it is useless to add pitfalls! This is a checklist and a few tips to start smoothly. Firstly , if you are accustomed to program and Python or another language leaves you completely indifferent , just take a look at the few traps described below and tackle down the Python tutorial of your choice .

On the other side,  if you back off, start by convincing yourself that it is not necessary to master Python in order to use it for our tasks with ArcGis. It is quite possible to link the processing in a Python script by only knowing the basics of the language .

Continue reading “ArcGis and Python (2 ): for a good start”