[Qgis-user] Edit vertex using DMS coordinates Plugin?

Fri Sep 11 14:32:17 PDT 2015

Hi Alexandre,

It is actually not a plugin.
It is part of an application which launched aside of QGIS to help the users to draw airspaces.
Their requirements are to work on the projected coordinate system with the data stored in world coordinate system but when they add geometries they want to input points in DMS format.

I build a Widget GUI using QtDesigner (see the picture)

The user enters start point of the line as: DD MM SS.XXX H, DD MM SS.XXX L
Where:
DD - degrees
MM - minutes
SS - seconds
XXX - decimals for seconds
H - is the hemisphere N or S
L - is the W for West and E for East

Then the drawLine is called  and executes the drawing of the line.

If I have time I will make a plugin. You are welcome to do it if you have more time than me.

Thanks,
Marian

From: Alexandre Neto [mailto:senhor.neto at gmail.com]
Sent: September-11-15 3:58 PM
To: Tudorache, Marian; Pedro Venâncio
Cc: QGIS User
Subject: Re: [Qgis-user] Edit vertex using DMS coordinates Plugin?

Making a plugin might be an idea. Or some improve the numericalvertexedit and numerical digitize plugins.

I will have a look into all your code.

Meanwhile, what is the name of your plugin? It sound useful fot mem.

Thanks

A 19h34 Sex, 11 de Set de 2015, Tudorache, Marian <Marian.Tudorache at navcanada.ca<mailto:Marian.Tudorache at navcanada.ca>> escreveu:
Hi,

I am sorry to interfere in this thread but I think my findings will help you.
I also want to report a possible bug.

I have worked to a plugin which display the coordinate in DMS when the user execute a mouse left click on the map.
When the geometries are displayed on the projection, the conversion on the fly to DMS does not work properly.
To have properly displayed the coordinate in DMS or Decimal degree you need to re-project your data to a coordinate reference system (WGS84 or GRS80, or other).

For example:
If data is displayed in projection reference system (stereographic in my case) and data is stored in world coordinates system (X and Y).
X = -1081940.67048 and Y = 2561405.89514 will be displayed as 140040’13.726 W. There is not such latitude2561405053’42.489 N

This is the projection: +proj=sterea +lat_0=53.5 +lon_0=-76.0 +k=1 +x_0=0 +y_0=0 +a=6381816.160744 +b=6381816.160744 +units=m +no_defs

The conversion is done by the function toDegreesMinutesSeconds from QsgPoint class.
It looks the function is not able to do to re-projection back to the spheroid. I think this is a bug.

The function toDegreesMinutesSeconds works properly if it is applied to Decimal degree coordinate.

What to be done!
First you need to reproject your data by using QgsCoordinateTransform .
Ex.
crs = qgis.core.QgsCoordinateRefernceSystem(<idCRS>, qgis.core. QgsCoordinateRefernceSystem.InternalCrsId) # if you use a customized coordinate reference system
prs = qgis.core.QgsCoordinateRefernceSystem(<idPRS>, qgis.core. QgsCoordinateRefernceSystem.InternalCrsId) # if you use a customized projected reference system
transformation = = qgis.core. QgsCoordinateTransform(crs, prs)

#transformation object is used to re-project your coordinates.
For example:
point = qgis.core.QgsPoint(X, Y) # X and Y are in world coordinate system meters
#apply transformation to reproject your point
reprojectedPoint = transformation.transform(point, QgsCoordinateTransform.ForwardTransform)
print reprojectedPoint #you will get the point in decimal degrees.
pointDMS = reprojectedPoint. toDegreesMinutesSeconds(3, True, True) #your will get the point in degrees minutes seconds with respect to crs

if you want to input DMS data then you have to do the same steps but in reverse:

1.       Convert DMS to decimal degrees;

2.       Apply QgsCoordinateTransform to decimal degrees so you get X and Y.

You can build a plugin based on this class. Check out the function drawLine where I input a lat and long in DMS format and write the line geometry in x/y format. If you have write your geometry in lat and long decimal degrees you do not have to apply QgsCoordinateTransform.

#spam_activate_map_background
import qgis
from PyQt4 import QtGui, QtCore

class LineGeometryDMSInput:
    def __init__(self):
        self.__prs  = qgis.core.QgsCoordinateReferenceSystem(100006, qgis.core.QgsCoordinateReferenceSystem.InternalCrsId)
        self.__crs = qgis.core.QgsCoordinateReferenceSystem(100000, qgis.core.QgsCoordinateReferenceSystem.InternalCrsId)
        self.__transformation = qgis.core.QgsCoordinateTransform(self.__ prs  , self.__ crs)

    def drawLine(self, lineStartDMS, lineEndDMS):
        start_Point = lineStartDMS.split(',')
        end_Point = lineEndDMS.split(',')

        startLine = (self.fromDmsToDecimal(start_Point[0], 5), self.fromDmsToDecimal(start_Point[1], 5))
        endLine = (self.fromDmsToDecimal(end_Point[0], 5), self.fromDmsToDecimal(end_Point[1], 5))

        line_start = qgis.core.QgsPoint(startLine[1], startLine[0])
        line_end = qgis.core.QgsPoint(endLine[1], endLine[0])

        pointGeomStartTransformed = self.__ transformation.transform(line_start, qgis.core.QgsCoordinateTransform.ForwardTransform)
        pointGeomEndTransformed = self.__ transformation.transform(line_end, qgis.core.QgsCoordinateTransform.ForwardTransform)

        layer = qgis.utils.iface.activeLayer()
        latestID = int(layer.featureCount())
        layer.startEditing()
        caps = layer.dataProvider().capabilities()

        if caps & qgis.core.QgsVectorDataProvider.AddFeatures:
            featureLine = qgis.core.QgsFeature(layer.pendingFields())
            geom = qgis.core.QgsGeometry.fromPolyline([pointGeomStartTransformed, pointGeomEndTransformed])
            #if your data is stored in geographical coordinate use this
            #geom = qgis.core.QgsGeometry.fromPolyline([line_start, line_end])

            featureLine.setGeometry(geom)
            layer.dataProvider().addFeatures([featureLine])

        layer.commitChanges()
        layer.updateExtents()
        layer.startEditing()
        qgis.utils.iface.zoomToActiveLayer()

    def fromDmsToDecimal(self, dmsString, precision):
        degree = float(dmsString.strip()[:2])
        decimal_minutes = float(dmsString.strip()[2:-9])
        decimal_seconds = float(dmsString.strip()[5:-2])

        decimal = round(degree + decimal_minutes/60 + decimal_seconds/3600, precision)
        if 'S' in dmsString or 'W' in dmsString:
            decimal = decimal * (-1.0)
        return decimal

Thanks,
Marian

From: qgis-user-bounces at lists.osgeo.org<mailto:qgis-user-bounces at lists.osgeo.org> [mailto:qgis-user-bounces at lists.osgeo.org<mailto:qgis-user-bounces at lists.osgeo.org>] On Behalf Of Alexandre Neto
Sent: September-09-15 8:24 AM
To: Pedro Venâncio
Cc: QGIS User
Subject: Re: [Qgis-user] Edit vertex using DMS coordinates Plugin?

I know NumericalDigitize and NumericalVertexEdit, but none of them allows the user to input coordinates in DMS formats.
We receive coordinates in many formats, and mostly in some form of Degree, minutes and deciimal Seconds, or Degree, and decimal minutes.
Normally I put the coordinates in a CSV and open it in QGIS to import the coordinates. But It would be nicer the be able to add/edit them directly in one of those format instead.
I did not know the node edit widget, looks interesting.
Thanks,
Alexandre
Em qua, 9 de set de 2015 às 12:22, Pedro Venâncio <pedrongvenancio at gmail.com<mailto:pedrongvenancio at gmail.com>> escreveu:
Hi Alexandre,
Anyone know if it's possible or if there is a plugin that allow one to introduce

Have you tried NumericalDigitize plugin?

and modify vertex using introducing Degree, Minutes and Seconds (or any other variation) values.

For editing, we have in QGIS master the new Node editor widget [0], which has the Vertex editor list (i).

I don't know if you can work with Degrees, Minutes and Seconds in any of them, but with decimal degrees they work well.
Best regards,
Pedro Venâncio

[0] https://github.com/qgis/QGIS/pull/2217

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