Essential
QGis operations in Roll
Adding a
point layer may be needed to show the requested survey outline from a client
(Area of interest), or a prospect outline from the geologist
1. In QGis: Layer à Add delimited text layer
2. Select filename
3. Optionally, give it a layer name
that is different from the file name
4. Check File Format
5. Check Record and Field Options (For
header lines etc.)
6. Define columns that represent X, Y
and optionally Z values
7. Finally, select “Add”
8. Using Full Zoom (Ctrl+Shift+F)
in QGis, you can now zoom to these points on the map
Once a point
layer has been created, you can find them as a series of “small dots” in QGis.
But these “dots” are hard to spot once you zoom out. It is therefore useful to
turn these points into lines.
1. In QGis: Processing à Toolbox will show (or hide) the
Processing Toolbox
2. Processing Toolbox à Vector creation à Points to path
3. Select Input layer
4. Create closed path (optionally)
5. Then, select “Run” to create a multi-line
in order the points are listed
The lines
are much better visible than points, but you cannot fill a line layer. To do
so, you need to convert the lines to a polygon.
1. In QGis: Processing à Toolbox will show (or hide) the
Processing Toolbox
2. Processing Toolbox à Vector geometry à Lines to polygons
3. Select Input layer
4. Then, select “Run” to create a filled
polygon
5. Double-click the polygon to show the
Layer Properties
6. Under “Symbology” adjust the Color
to a meaningful color
7. Reduce Opacity to less than 100% to
see features in underlying layers
8. You can also add an outline to the
polygon. To do so:
a. Add a Symbol Layer by pressing the
green “Plus” Icon
b. For symbol layer type select:
“Outline: Simple Line” (Sits at the bottom of the list)
c. Select appropriate color and Stroke
width
d. Select OK
9. Finally, in Layers Panel à context menu of the created
layer à
Make permanent
10. When an outline has been added to
the polygon; you may delete the line layer. The line layer served its purpose
(creating a polygon) and is no longer needed for the following steps, where we
edit the exported src/rec/sps/rps data in QGis.
1. In Roll: File à Export to QGis à Export Geometry à Export xxx Records to QGis
2. Alternatively: SPS import tab à Export to QGIS buttons for SPS and
RPS records
3. Alternatively: Geometry tab à Export to QGIS buttons for SRC and
REC records
4. This will create in-memory
(“scratch”) layers in QGIS with the exported data
To make the
exported source and receiver data permanent, and available when you open the QGis
project the next time, follow the steps below
1. in Layers Panel à context menu of the scratch layer
à Rename
layer
2. Use Ctrl+C
to copy the layer name. Hit escape, and do not rename
3. in Layers Panel à context menu of the scratch layer
àMake
Permanent
4. Alternatively à push the ‘scratch’ button on the
right side of the layer’s name
5. Select ESRI Shapefile as file format
6. Select ellipses ( … ) next to
filename à navigate
to desired file location in the dialog
7. Paste the “filename” from clipboard
in the dialog’s “File name” field
8. Select ok. The layer is now
permanent, and will be restored if the project is opened again.
To make
changes to any of the layers you need to enable editing. To do so:
1. in Layers Panel à context menu of the layer with point
data from Rollà Toggle
editing
2. A pencil icon will appear left of
the layer name.
3. The pencil on the digitizing toolbar
will also be highlighted.
4. In the digitizing toolbar select the
Vertex tool for the current layer. This allows you to manipulate vertices on
the active layer using one of the following methods:
·
Right
click to lock on a feature
·
Click
and drag to select vertices by rectangle
·
Alt+click to select vertices by polygon
·
Shift+click/drag to add vertices to selection
·
Ctrl+click/drag to remove vertices from selection
·
Shift+R to enable range selection
Once
changes have been made to point locations in QGis (or when points have been made
inactive, or have been deleted) it can be useful to read these points back
into Roll, to rerun analysis for Binning of Geometry data, or binning of
imported SPS data. To lod modified point data back
into Roll:
1. In Roll: Geometry tab à “Read from QGIS” buttons (for SRC
and REC data separately)
2. In Roll: SPS import tab à “Read from QGIS” buttons (for SPS and
RPS data separately)
3. In the layer dialog that pops up:
a. Select the correct point layer from
QGis, containing SPS/RPS and SRC/REC data
b. Check that the CRS of the selected point
layer matches that of the Roll project
c. Decide whether (or not) to use a selection
field code. Normally this is the “inuse” field.
d. To see what fields are available in
a point layer in QGis, you can:
i. In Layers panel à Select the appropriate layer
ii. In context menu à Open Attribute Table (Shift+F6)
iii. Check column headers. Roll expects
the following fields:
‘line’, ‘stake’, ‘index’, ‘code’, ‘depth’, ‘elev’ and’
inuse’
iv. ‘inuse’ =
0 is used to deselect a point for analysis in Roll
To update
the analysis results in Roll:
4. In Roll’s processing menu à Binning from Geometry or Binning
from Imported SPS
In Roll,
survey geometry created is created using one or more rectangular blocks. In
reality, a survey rarely consists of one or more rectangular shapes, but its
outline is truncated according to the concession boundary, or impacted by
features such as cities, lakes, etcetera. So, it will be necessary to cut
(completely remove) or to switch off (mute) points in certain areas. In QGis
this can be done by checking if points fall inside a polygon. There are two
obvious solutions:
Clipping
will remove all points outside a selected polygonal area. It is quick and easy,
but won’t allow for points to be reinstated at a later stage; gone-is-gone.
This can be cumbersome when the survey area is being finetuned over several
iterations. Steps are straightforward:
1. Vector à Geoprocessing Tools à Clip …
2. Select Input layer: the layer containing
SPS/RPS or SRC/REC points
3. Select Overlay layer: the layer with
the boundary polygon
4. Select Run
5. The clipped point layer is now
created as a scratch layer.
This
approach first selects all points that lay inside a polygon, and is followed by
turning the selection flag into a permanent attribute value (normally applied
to “inuse”)
1. Vector à Research Tools à Select by Location …
2. Select features from: chose
appropriate SPS/RPS or SRC/REC point layer
3. Where the features “are within” (and
optionally “touch”)
4. Select the appropriate polygon layer
5. Create a new selection
6. Then, select “Run” to create a
selection of points inside a polygon
7. These points will be highlighted in
yellow and marked with a red cross
8. Now from the Attributes toolbar à Open Field Calculator
9. Alternatively: F6 to open Attribute
Table, followed by Ctrl+I to Open Field Calculator
10. Uncheck “Only update xxx selected feature(s)”. We need
to update all features, also those that have not been selected. If you forget
to do so, only the already selected records will be altered, and in the
unselected fields a NULL value will entered
11. Either (a) Create a new Field, with
a 32 bit integer and default field length or (b) update an existing integer
flag, such as the “inuse” field
12. In the Expression widget type the
following:
is_selected()
This function returns true
(=1), when a point record has been selected, and false (=0) otherwise.
13. Press “OK” and let the operation run
on all point records of the active layer.
14. Upon completion, check that
everything went according to plan in the Attribute Table (F6)
15. Now the point layer is ready to be read
back into Roll (See par above).