Really Stefan these were my main doubts.
- if someone loads a shapefile (or raster) with geographic coordinates
stored your change would still be showing meters (or do I misunderstand
your proposal?).
Right now Coordinatelistmetrics always shows units as if they were metric
even on geographic coordinates. The test, try to open a EPSG 4326 wms
service and digit a linestring or polygon. On lat/lon maps distance/area
displayed on bottom bar are not true, Angles are not corrected.
- what happens if the user has for instance everything in "cm" or "mm" as
he may work with some really tiny stuff (e.g., model trains?). What happens
then? How will you be able to display the right units when you add "m"?
That is also what happens also with the AdvancedMeasure tools: if you
measure on a mm or cm map the output will always show "m".
Even having a valid project coordinate system means a huge work to change
many plugins, calculate area, perimeter, statistic tools, advancedmeasure
tools, etc...
The only solution, most simple one, is an option panel which allows user to
choose a) Unit of the map and b) Unit of measures c) relative scale, like
gvsig or Kosmo. So user don't have to care about the crs. For lat/lon maps
there are other solutions, just give a look at last version of
measureextension plugin (
http://sourceforge.net/projects/opensit/files/Openjump/PlugIn/MeasureExtension/
)
Peppe
2013/2/14 Stefan Steiniger <sst...@geo.uzh.ch>
> Hi Peppe,
>
> I am not sure if you can do the changes without knowing about the SRID/
> project coordinate system.
> For instance if someone loads a shapefile (or raster) with geographic
> coordinates stored your change would still be showing meters (or do I
> misunderstand your proposal?). Also, what happens if the user has for
> instance everything in "cm" or "mm" as he may work with some really tiny
> stuff (e.g., model trains?). What happens then? How will you be able to
> display the right units when you add "m"?
>
> just some thoughts,
>
> cheers
> stefan
>
> Am 14.02.13 14:21, schrieb Giuseppe Aruta:
> > Immagine in linea 1
> > Hi all
> > I want to do some modifications on class CoordinateListMetrics. This
> > class is basically used to show angle/distance/area of a shape when a
> > cursor tool is actived (drawing or measure tools) an the left side of
> > buttom bar.
> >
> > This is the actual dispaly from CoordinatesListMetrics not modified
> > Immagine in linea 1
> >
> >
> > And this are the display modifications I want to add
> > Immagine in linea 2
> >
> > As you can see there will some extra informations:
> > - Distance will show the total length + length and (in the breaks)
> > between last click and cursor position. I took this idea from OpenJUMP
> > the Merge
> > - Display will show also the Azimuth between last click and the cursor
> > position
> > - All measurements show International Standard Unit (meter for lenght,
> > square meter for area and Decimal Degrees for angles. All measure will
> > be calculate till 2 decimals
> >
> > If someone wants to see how it works, I adopted this way to display info
> > on my MeasureTools plugin building a modified copy of
> > CoordinateListMetrics (and copies of conresponding classes
> > Multiclicktool, PolygonTool, etc)
> >
> > ------------------------------------------------
> >
> > Which are the pros
> > - User has a better control on what is drawing (or measuring) and the
> > can understand the scale of the shapes on the view, decide the length of
> > last drawn segment of a polygon, choose the angle and the azimuth of
> > segments.
> > - The information are more clear about that is going on "under the
> > cursor tool"
> >
> > the cons
> > a) These measure are shown only on SI units so some users who work with
> > Inperial Unit will feel disadvantaged
> > 1st Solution - Actually we have a Measure on feet tool which calculates
> > only distance in feet (from meter unit maps) I will also add an extra
> > tool on menu which will calculate also the area in Imperial Unit (I ask
> > to Landon which is the most common used square feet or else)
> > 2nd solution - In the future I will study an option will allows user to
> > choose either map units (if necessary) and measure units on OpenJUMP.
> >
> > b) The actual algorithm on CoordinateListMetrics (included up to come
> > Azimuth) work on Cylindrical projections and fail to calculate
> > measurement when coordinates are expressed in lat/lon coordinates and/or
> > not cylindrical projections.
> > Solution - In the up to come MeasureTool ther will be tools which will
> > calculate Area/Bearing using extra algorithms (MeasureTool 0.7 already
> > has a measure length tool using Thaddeus Vincenty's inverse formula).
> > This is a partial solution and, more than this, I belive there are not
> > so many people who want to work on lat/lon map.
> >
> > Before doing these modifications I would like the opinion of the other
> > OpenJUMP community members. Regarding Translation, the only code I will
> > add will be "Azimuth".
> >
> > Regards
> >
> > Peppe
> >
> >
> >
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