The presentation is an assignment done during the course of the subject.

1. Geo-referencing / Digitization in Q-GIS
Lakshya Pandit
15554007
M.Tech (Infrastructure Systems)
IIT Roorkee

2. Objective
To geo-reference and digitize the current map of the IIT Roorkee campus (dated 1998), post geo-referencing and adding
relative attributes of the layers to be added.

3. Methodology

4. I. Geo-referencing of the Map
• For the geo-referencing of the map, the co-ordinates based on the UTM, are saved and collected from the on-site analysis
by the help of the GRX-2 Sokkia instrument.
• The 14 points located on the map, are dealt with on-site check-up of the respected points with 15 minutes of stationary
time for each point respectively, setting the receiver height at 1.9m from the ground level, and epoch rate less than 5.
• Based on the given map, the points were noted and the data of the co-ordinates were taken into consideration for the
geo-referencing of the map.
Map of IIT Roorkee_1998 Map of IIT Roorkee_1998 (14 Points for geo-referencing)

5. • The data collected post site-analysis is recovered through the survey spectrum software.
• The zone setting of the co-ordinate system is 43 N , as roorkee falls under the specific zone; and the Co-ordinate type set
is WGS (World Geodetic System _84)
• With the 95% confidence level for the GPS post processing, the report is generated in the HTML format, with Ground
Northings and Ground Eastings data collection as follows :
Report

6. Report

7. Report

8. • Based on the Ground Northings and Ground Eastings of the report data, the points are referred into the
Q-GIS 2.8.5 Wien version through following steps.
• Geo-referencer under the raster edit tool bar is clicked.

9. • For Georeferencing, first new raster layer is to be
added i.e the existing scanned map of the IIT Roorkee
campus, which is in the .png format.
• The Co-ordinate reference system for the Map is to be
set as WGS 84 / UTM zone 43N
• Once the Map is generated, the points on the map are
to be marked with the required Ground Northings and
Ground Eastings as per the figure in the bottom right
corner.
• During the marking of the points, the emphasis is to be
paid on the marking of the points, which should be
done such that two consecutive points lay at the
farthest opposite ends to each other.
• This ensures the plane nature of the map comes into
play, therefore leading to less distortion in the map,
during the geo-referencing.
• For example, after point 1 i.e on the upper north end of
the map, point 2 i.e. at the lower southern end of the
map is poined, then point 3 at the western end of the
map followed by point 4 at the eastern end and so on.

10. • Once all the points are put on the map, based on the
UTM system, the transformation settings are to be
adjusted before the initiation of the geo-referencing.
• Transformation type is based on the frequency and
accuracy of the points noted in the georeferencer.
Polynomial 1 is selected.
• Transformation setting determines how the ground
control points are used to transform the image from
source to destination coordinate space.
• Default setting of Resampling method i.e. Nearest
Neighbour is taken into consideration. This determines
the pixel value of the output raster.
• The Output raster is the location where the
georeferenced file will be saved. Accordingly, the
location is set up and the WGS 84 / UTM zone 43N is
selected under the Target SRS.
• Once the transformation settings are set, the
Georeferencing can be initiated. This lead to the
following georeferenced image at the bottom right
corner :

11. • Post geo-referencing in order to check the map, it is
opened via new project through a new raster layer.
• In order to super-impose the map w.r.t the satellite
image, openlayers plugin via web tool is assessed.
• Through this, the Google satellite is chosen for the
correlation of the location w.r.t the map.
• Once the layer is added, the transparency of the raster
map (georeferenced) layer is temporarily set from 30-
60%, which is accessed through the property dialogue
of the raster layer.
• Post setting of the layer, the location matches with the
georeferenced map of the campus, therefore this can
now be utilized for the digitization in the QGIS for
further stages.
• It is to be made sure that the co-ordinate reference
system for the map lies in the WGS 84 / UTM zone 43N

12. Figure : Correlation of the Google satellite with the Georeferenced Map of IIT Roorkee

13. II. Digitization
• Post geo-referencing , the next step is the digitization.
• The Map includes Roads, Infrastructure elements like
buildings, grounds etc, which are to be digitized.
• These are added through layers via SpatiaLite Layer
dialogue box under the Create Layer tool bar within
Layer.
• In order to start with building as a layer, a database it
to be set up, which records the attributes and other
elements within its directory.
• The database location is set up, leading to the Name of
the layer i.e Building in this case. The geometry being
a polygon, Type – Polygon is selected. The CRS is
checked to the WGS 84 / UTM zone 43N.
• The next important step is identifying the attributes
related to the building, and their Type. For example,
Name of the building will have Text type, whereas the
Ground coverage will have the decimal type within the
attribute system.
• Post defining the attributes of the Layer i.e Building,
Digitization initiates.

14. • The initial step is to make sure the snapping options is
checked with respect to all Layers to decrease the
degree of error during the digitization process
• Once the Snapping Option is checked, the digitization is
started within the Toggle editing mode.
• Toggle editing mode is accessed as shown in the
bottom right image as follows.
• This activates the editing options within the Building
layer which help in digitizing the map.
• By using the Add new feature tool in the upper tool
panel, the polygon can be started to develop in shape.
• The properties related to the Building layer can be
accessed in the Properties dialogue box.

15. • Using Add feature, the polygon shaping takes into
place, which can be taken from clockwise /
anticlockwise direction.
• Once the polygon is completed, right clicking,
terminates the shaping of the polygon by joining the
last point with the first point automatically.
• Post completion of the Polygon, Dialogue box appears
where the attributes of the building are to be filled, i.e.
the Name, Type, Ground coverage etc.
• With respect to the type of building the information is
added.
• In case of a courtyard the polygon is to be modified.
• This is achieved using the Add ring command in the
upper tool panel, in a similar fashion as with the add
feature.

16. • Opening within a polygon is done with utilization of the
Add Ring feature.
• It is utilized in similar fashion with respect to the Add
new feature tool command.
• With help of advanced digitizing tool, the cuts are
made more accurate based on the orthagonal nature
of the lines selected.
• Hence, this helps in increased perfection of the
geometry of the particular polygon.
• Once the polygon is complete, but still needs some
minor changes, Node tool in the tool panel can be
utilized to modify individual nodes of the polygon.
• On the completion of the polygon, the attributes of the
building with respect to the area / perimeter of the
polygon can be assessed using the commands within
the attribute table.

17. • In order to add the area feature within the ground
coverage, the attribute field calculator can be utilized.
• Selecting the Ground coverage as the attribute, the
area function within the expression box can be
accessed.
• The Area function under the Geometry Title is to be
selected with double click, which adds the function as
$area on the empty left box.
• On the addition of the area command, the update field
selection can be added which later updates all the
values under the Ground coverage attribute.
• This shows the resultant area of the polygon as shown
in the adjacent figure, where the area of the Main
building Polygon is shown.
• Similarly various buildings can be updated with
respected to their attributes within this section.
• In case of Road Layer, instead of Polygon type , Line
type is to be selected while adding the layer to the
database.

18. Figure : Buildings digitized as on 15.02.2016
Figure : Buildings attribute sample of the buildings digitized

19. Post Digitization / Road Graph Analysis in Q-GIS
Lakshya Pandit
15554007
M.Tech (Infrastructure Systems)
IIT Roorkee

20. Objective
To analyze the shortest path through road graph post digitization of the the current map of the IIT Roorkee campus (dated
1998).

21. • The adjacent picture shows the
digitization of the building
infrastructure along with the
respective attributes .
• The attributes include Type of the
building, number of floors, Ground
coverage area and Name of the
building.
• A total of 355 polygon vectors were
generated under the building
infrastructure layer.
• The adjacent attribute tables show the
characteristics of the building
infrastructure digitized.
Building Infrastructure

22. • The adjacent picture shows the
digitization of the Landscape
infrastructure along with the
respective attributes .
• The attributes include Name and
Ground area of the respective layer.
• A total of 110 polygon vectors were
generated under the landscape
infrastructure layer.
• The adjacent attribute tables show the
characteristics of the landscape
infrastructure digitized.
Landscape Infrastructure

23. • The adjacent picture shows the
digitization of the Road
infrastructure along with the
respective attributes .
• The attributes include Name, width,
speed, direction and length.
• A total of 270 line vectors were
generated under the road
infrastructure layer.
• The adjacent attribute tables show the
characteristics of the road
infrastructure digitized.
• In the direction attribute, 0 signifies
two-directional, whereas -1&+1 signify
one directional forward and reverse
flow.
Road Infrastructure

24. • The adjacent picture shows road graph
setting for the shortest path analysis.
• For the analysis, in the transportation
layer, the layer selected is road, and
the direction layer is utilized under the
direction field.
• Similarly for the speed field, the speed
attribute of the road layer is selected,
where different road segments have
different speeds.
• The adjacent picture depicts the
selection of shortest path under the
panel table.
• In the direction attribute, 0 signifies
two-directional, whereas -1&+1 signify
one directional forward and reverse
flow.
Road graph

25. • The adjacent picture shows the
selection of the abn junction as the
start coordinate and hospital as the
stop coordinate.
• For the analysis, the time is taken as
the deciding factor for the shortest
path analysis.
• The total length of the shortest path
based on time is 1.09635km.
• On calculation the following path(red)
is generated.
• The total time of the shortest path
based on time is .0297555 hours i.e
approximately 2 minutes by car.
Shortest path analysis

26. Sheet Layouts