GIS coaching for territorial management.
Following innovations introduced by QGis version
2.12 : as in Excel tables, now
you
can
control
the cells setting of the attribute table
of a layer .
Now you can apply
conditional rules on the format implementation of
the attribute table. To this end , open the
attribute table of a layer
. On the right, you will see a new
button for the conditional setting.
Continue reading “Conditional formatting of attribute tables with QGis 2.12”
QGIS cloud is a free platform to upload online and share your maps with anyone . QGis advantage is to have the chance of preparing your own maps using Qgis and upload them online in a few clicks .
You will need to create a QGis Cloud account ( free , simple, quick) and install the QGis cloud plugin in your QGis version.
Continue reading “How to publish your QGis maps in the web with QGis Cloud”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”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:
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 .
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.
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.
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)”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 !”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”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”