Celebrating Our Woodland Heritage QGIS 2.18.14 Manual · 1 Celebrating Our Woodland Heritage: QGIS...

0 Celebrating Our Woodland Heritage: QGIS 2.18.14 Manual

Report No: PP6/060517

Celebrating Our Woodland Heritage QGIS 2.18.14 Manual

Pennine Prospects

Celebrating Our Woodland Heritage Project




Celebrating Our Woodland Heritage

QGIS 2.18.14 Manual

Pennine Prospects



Compiled by Christopher Atkinson BA (Hons), MA

Woodland Heritage Officer


December 2017

Pennine Prospects

Hebden Bridge Canal & Visitor Centre

Hebden Bridge

West Yorkshire

HX7 8AF



About the Author and Pennine Prospects

At the time of this report’s production, the author Christopher Atkinson was in

employment with Pennine Prospects as part of the Celebrating Our Woodland

Heritage Project. As Woodland Heritage Officer, Chris was tasked with carrying out

a programme of archaeological woodland surveys across the South Pennines. Chris

has been in full time employment as an archaeologist since 2006, during which time

he has been employed by Herefordshire Council’s archaeology service as

Community Archaeologist (2006-2013); Project Officer for the National Trust (2015)

and self-employed (2013-2016).

He is experienced in landscape survey, site excavation, geophysical survey, desk-

based assessment, use of GIS techniques (including MapInfo Professional; ArcGIS

and QGIS) and the production of management plans for clients such as Natural

England and Historic England. Chris holds an undergraduate degree in Archaeology

from the University of Wales Lampeter (2004) and a Masters with distinction in

Landscape Archaeology from the University of Sheffield (2015).

Pennine Prospects is a unique rural regeneration company created in 2005 as a

champion for the South Pennines, the dramatic upland landscape that stands

prominently above the urban centres of Greater Manchester, the Lancashire valleys

and West Yorkshire. It is an award-winning partnership organisation that has

attracted over £5 million of national and European funding to deliver a wide range of

projects aimed at promoting, protecting and enhancing the built, natural and cultural

heritage of the South Pennines.

Pennine Prospects lies at the heart of a well-established partnership bringing

together six local authorities, two water companies, government agencies and the

voluntary sector. The company is strongly committed to sustainable development

and enables partner organisations, local residents and businesses to maximise the

benefit of the area’s rich natural, cultural and heritage assets.

Through its activities, Pennine Prospects supports the economy of the South

Pennines by uncovering, highlighting and promoting all that is special about the area.

In addition, the company develops community projects, promotes access to the

uplands and waterways and connects people with their landscape.



Contents

Introduction

1.0 Setting Up A New Project 6

2.0 Using Vector Data

2.1 Importing Vector Data 8

2.2 Managing Vector Data 10

2.3 Labelling Vector Data 12

2.4 Adding Attributes to Vector Data 13

2.5 Creating Point Vector Data from Survey Data 15

2.6 Creating Polygon Vector Data 18

3.0 Using Raster Data

3.1 Importing Raster Data 22

3.2 Georeferencing Raster Data 24

4.0 Using Light Detection and Ranging (LiDAR)

4.1 Importing LiDAR Data 29

4.2 Slope Modelling 31

4.3 Hillshade Modelling 34

5.0 Creating and Saving a Map

5.1 North Arrow 37

5.2 Scale Bar 37

5.3 Legend 38

5.4 Text Box 39

5.5 Save Map 39



Introduction

This report has been compiled as part of the Celebrating Our Woodland Heritage

project. This three year project (2016-2019) is jointly funded by Yorkshire Water,

Heritage Lottery Fund, Green Bank Trust and Newground Together and aims to

identify record and interpret the historic environment of woodlands across the South

Pennines (National Character Area 36 – Natural England, 2014).

Led by Pennine Prospects, the project recognises as a result of a desk-based study

‘Hidden Heritage of the South Pennine Woodlands’ (Brown, 2013), that … “number

of sites recorded on the HER (Historic Environment Record) does not represent the

true nature of the surviving archaeological resource”. The report highlighted that this

underrepresentation (and general lack of knowledge) was the primary threat to

woodland archaeology.

The Celebrating Our Woodland Heritage project therefore seeks to enhance the

historic record for woodland across the South Pennines by means of a structured

programme of archaeological walkover surveys. Where appropriate these surveys

will provide the opportunity for members of the public, heritage and youth groups to

engage and contribute towards the investigations.

Archaeological features to be recorded within areas of woodland can represent the

whole of human history and use of the landscape. Features relating to the woodland

itself can include historic or veteran trees; woodland boundaries; charcoal burning

platforms; storage platforms; cottage sites; trackways and mills. Features may also

predate the current woodland and represent prehistoric-medieval field boundaries;

settlement sites or stones such as Bronze-Age cup and ring carvings.

The information collated during the field surveys will be deposited in the form of an

archaeological report and digital record to the landowner and the regional Historic

Environment Record. This data will not only guide future research into the region,

but also support and promote the preservation of the historic environment as a part

of any future management programmes within woodlands.

This manual is aimed at individuals interested in enhancing their archaeological skills

providing an introduction to Geographical Information Systems (GIS) and its uses in

archaeology.



QGIS is a great piece of Open Source (FREE) software that meets all the basic

mapping and analysis requirements of most archaeologists. It offers individuals a

platform to visualise survey data, display mapping data (such has historic maps) and

utilise Light Detection and Ranging (LiDAR) files produced by the Environment

Agency and now made Open Source. Ultimately GIS is a tool, providing the

individual with the opportunity to store, edit, analyse, display, share and publish their

investigations at a professional standard.

From landscape surveys and field walking to geophysical surveys and excavations,

GIS software is a must have tool in the archaeologists arsenal. To follow this guide

you can download the Open Source digital files from the Celebrating Our Woodland

Heritage project website at: http://www.celebrate-our-woodland.co.uk/

Below is a useful list of links from which you can obtain all of the Open Source data

you require to get you started on your own GIS projects:

GIS Software

Download QGIS for your platform

http://www.qgis.org/en/site/forusers/download.html

Opendata

Ordnance Survey Data

https://www.ordnancesurvey.co.uk/opendatadownload/products.html

LiDAR and Orthophotographic Data

http://environment.data.gov.uk/ds/survey/index.jsp#/survey

Historic England Listing Data

https://historicengland.org.uk/listing/the-list/data-downloads/

Natural England Data

http://www.gis.naturalengland.org.uk/pubs/gis/GIS_register.asp

Historic Maps

http://www.oldmapsonline.org/; http://maps.nls.uk/

Please be a aware of copyright infringements regarding the use of historic maps

http://www.celebrate-our-woodland.co.uk/

http://www.qgis.org/en/site/forusers/download.html

https://www.ordnancesurvey.co.uk/opendatadownload/products.html


https://historicengland.org.uk/listing/the-list/data-downloads/

http://www.gis.naturalengland.org.uk/pubs/gis/GIS_register.asp

http://www.oldmapsonline.org/

http://maps.nls.uk/



1.0 Setting up a new project

Open QGIS Desktop 2.18.14 with GRASS 7.2.2 (you may have to wait a couple of minutes

for the software open).

Close the QGIS Tips window when it opens.

Figure 1: You should see a window like this above

To begin click on Project (found in the horizontal toolbar at the top of the page) and

select Project Properties (figure 1).

A window will open, from which you can set the basic requirements of the new

project (figure 2). First visit CRS (listed on the left hand side). This allows you to set

the Coordinate Reference System.

First tick Enable ‘on the fly’ CRS transformation (OTF) which means you can use

data which have multiple coordinate systems in the same project. We will be using

the British National Grid as our coordinate system. Find OSGB 1936 / British

National Grid EPSG: 27700 from the list and select Apply (if searching for the first

time you may have to check the Coordinate reference systems of the world box).



Figure 2:

Project

Properties

CRS

Then select General from the left hand side of the Project Properties window. Here

we need to make sure the Save Paths option is set to relative (figure 3). Doing this

allows us to move a folder from one location to another without breaking file links.

Press OK to

finish

Figure 3:

Project

Properties

General

When complete, click on Project and select Save As.

Save the file within the GIS Workshop Data folder under the name Hirst Wood.



2.0 Using Vector Data

What is Vector Data?

Vector data provides a way to represent real world features within the GIS

environment. A feature is anything you can see on the landscape. A vector feature

has its shape represented using geometry. The geometry is made up of one or more

interconnected vertices. A vertex describes a position in space using an X, Y

(Easting and Northing) and optionally Z axis (Height).

A feature with a single vertex (such as a find spot, tree or charcoal platform) is

known as a point feature.

Where a feature’s geometry consists of two or more vertices and the first and last

vertex are not equal (such as a river, track, ditch or boundary) a polyline feature is

formed.

Where three or more vertices are present, and the last vertex is equal to the first, an

enclosed polygon feature is formed (such as an area of woodland, lake or building).

Vector data also includes attributes, which consist of text or numerical information

that describe the features.

Point Data Polyline Data Polygon Data

2.1 Importing Vector Data

On the saved Hirst Wood project select the Add Vector Layer icon (figure 4). This

will open the Add vector layer window (figure 5), click Browse and select the Natural

England Data (figure 6) and then Clipped Ancient Woodland v3.shp.

Figure 4



Figure 5

Press Open on the Add Vector

Layer window. After a moment

you should see a scattering of

polygons relating to the location

of semi-ancient natural woodland

across the South Pennines.

Figure 6

We will now start to build up our

map of Hirst Wood. Following the

same routine as above we will now select the OS Opendata 50m Contour folder

and import the vector layer SE13_line.shp. You will notice a grid of contour lines

appear on your map. To zoom in on this layer, right click on the layer labelled

SE13_Line listed on the left of the screen in the Layers Panel and select Zoom to

Layer (figure 7).

Figure 7

We now need to add Ordnance Survey data relating to roads, buildings, railways,

rivers and woodland. Repeat the process and select OS VectorMap District (ESRI

Shape File) SE, then Data and open the layers:



SE_Building.shp

SE_RailwayTrack.shp

SE_Road.shp

SE_SurfaceWater_Area.shp

SE_SurfaceWater_Line.shp

SE_Woodland.shp

Figure 8: On completion your map window should look something like this

2.2 Managing Vector Data

You will notice that each of the shapefile layers added are a mixture of polyline and

polygon data. Using the Layer Panel on the left of the screen we need to rearrange

the data so that each layer is visible in its entirety.

Left click and drag each layer so that the polygon data is at the bottom and the

polyline data is at the top. Make sure the contour layer SE13_line is at the top.

Figure 9



Figure 10 Figure 10: Layer Properties window displaying style page

We now need to change the colour of each layer. To do this either right click on a

layer and select Properties from the drop down menu, or double click on the layer to

open the Layer Properties window (figure 10).

Open the properties window for the Polygon layer SE_Woodland and select Style to

change the colour of the layer. You can either select a costum colour or use on of

the predefined colours. When you are happy with the colour press OK.

Repeat the process for the other vector layers.

Press Save.



Figure 11: On completion your map may resemble something like this.

2.3 Labelling Vector Data

Selecting the SE13_line contour vector layer we will now display height data

alongside the contours. This information is saved within the layers attributes.

Reopen the Layer

Properties window

and select Labels

(figure 12).

Figure 12: Layer

Properties window

displaying labels page.

In the top bar select

Show labels for this

layer and then Label

with 1.2

PROP_VALUE. You

can also select the

colour and size of

the text in this

window. When



complete click OK.

2.4 Adding Attributes to Vector Data

Attributes within Vector Data are sub-sets of information unique to each point,

polyline or polygon produced. At a basic level an attribute is a grid reference in the

form of an easting and a northing. But attributes can also represent a sites name,

and site type (such as woodland, field, moorland) and even descriptive information.

We are going to add a new field to the SE_Woodland Attribute Table, this will allow

us to label Hirst Wood.

1. Right click on SE_Woodland and select Open Attribute Table from the drop

down menu.

2. Select the Toggle Editing Mode icon (a yellow pencil in the top left hand

corner of the attribute table – see below left).

3. Select the New Field icon (a small table with a yellow star towards the right of

the menu bar – see below right).

4. In the Add Field table write Name in the Name

column, set the Type to Text (string) from the

drop down menu and increase the Length from

0 to 50 and press OK (right).

5. Once complete Save the table and close it.

6. Using the Information icon click on the

polygon of Hirst Wood.



7. Right click on the column Name in the Identify Results panel and select Edit

Feature Form from the drop down menu.

8. Type Hirst Wood into the Name column and press OK.

9. Finally Save the edits and press the Toggle Edit Mode icon on the main

project page to end editing session.

You can now label the wood on the Map Window via the Labels page in

Properties.

Press Save.

2.5 Creating Point Vector Data from Survey Data

As part of the Celebrating Our Woodland Heritage project we have been collecting

information concerning previously unrecorded/unrecognised archaeological features

within woodland. Many of the features have consisted of small to large scale

quarries, charcoal burning platforms, trackways, drystone walls and woodland bank

and ditches. As part of the recording process we have noted each features grid

reference, its type, a general description and notes concerning its condition. All of

this information is essential in understanding the history and condition of woodland

archaeology across the region.

The collated field data is transferred into a digital spreadsheet format for use in

reports. This data can also be used to create point vector data, which can be

overlain onto our GIS map layers. This is useful for accurately displaying the

location of the identified archaeological features, as well as comparing the results

with any historic map layers, aerial photographs and LiDAR tiles.

To create Point Vector Data from an EXCEL Spreadsheet:

1. Open the EXCEL spreadsheet Hirst Wood Archaeological Survey

Database and save it as a CSV (Comma Delimited) file (Figure 13).

2. In your QGIS project window, select the Add Delimited Text Layer icon

found on the left had side of the window.

3. This will open the Create a Layer from a Delimited Text File window (figure

14). Click Browse to select your EXCEL CSV file. Make sure the CSV

(comma separated values) box is ticked and the x field contains Easting

and the y field Northing. Press OK.

4. The survey data should now be plotted on your map as dots (Figure 16).



Figure 13: Save the Excel spreadsheet as a CSV file.

Figure 14: Create a Layer from a Delimited Text File window.



5. If the data is not displayed, it probably means it has been created using the

wrong Coordinate Reference System. To correct this, right click on the

layer listed in your Layers Panel and select Set Layer CRS from the drop

down menu. In the Coordinate Reference System Selector window change

the CRS to OSGB 1936 / British National Grid EPSG: 27700 and press OK.

6. You now need to save the data as a Point Vector file (shapefile). Right click

on the layer listed in your Layers Panel and select Save As (figure 15 below

left).

7. This will open the Save Vector Layer file As… window (figure 15 below

right). Click Browse to choose a location and name for the file, make sure

the CRS is set to OSGB 1936 / British National Grid EPSG: 27700 and

press OK.

8. You have now created a Point Vector Layer. If you press the icon you will

be able to open each point’s attributes table and look at the information

produced as a result of the survey.

Figure 15

Press Save.



Figure 16

We will now alter the way the Hirst Wood Archaeological Survey Database data is

displayed by displaying numbers relating to Site Number and colours relating to Site

Type, as listed in the datas attributes.

1. Open the layers Layer Properties and select Style.

2. From the dropdown menu at the top of the window select the option

Categorized.

3. You will notice the window has changed. From the dropdown menu second

from the top and named Column, select the title Site Type.

4. Click the button Classify at

the bottom left hand corner of

the large white box. This will

result in a list of Site Types

appearing alongside

representative colours (you

can change the colours here

by double clicking each

circle).

5. When you are happy press

Apply and select the Labels

tab from the left hand column.

6. Following the steps outlined

on page 12-13, label the layer

selecting Site No.

7. Press OK (Figure 17).



Figure 17: Survey point vector data presented as categorised with Site Type represented as

different colours and labelled by Site No.

2.6 Creating Polygon Vector Data

Creating polygon vector data is really useful for highlighting areas of interest, such

as the extent of an area of ridge and furrow identified during a survey; or the footprint

of a building. As part of the Celebrating Our Woodland Heritage Project we have

been creating polygon vector data shapefiles for the purpose of illustrating historic

map data.

Once historic maps have been georeferenced (See 3.2 Georeferenced Raster

Data) creating polygon vector shapefiles for each map layer allows for the production

of standardised map layers, ideal for reporting and publication.

We will now import your the georeferenced raster map file Yorkshire 201 1842-52

Ordnance Survey Six-Inch England and Wales_modified contained within the

COWH GIS Workshop Data (See 3.1 Importing Raster Data for directions).

Once the historic map layers are display (make sure all other map layers are

switched off) we need to create a New Shapefile Layer.

1. Press the New Shapefile Layer icon located near the bottom of the left column

of the window. It should look like this:



2. This will open the New Shapefile Layer window (Figure 18).

3. Under Type, make sure Polygon is selected.

4. Beneath File encoding, select Project CRS (EPSG:27700 – OSGB 1936 /

British National Grid) from the drop down menu.

5. We now need to add ‘New Fields’ before it is ready. These represent the

polygon attributes. We want to add attributes/fields called Site Name and

Type.

6. In the box listed as Name, type

Site Name.

7. Make sure Text data is selected in

the drop down menu under Type.

8. In the Length box change the

number to 200 (this represents

how many characters will be saved

in the attribute/field, 200 is the

maximum).

9. Press the Add to fields list.

10. Repeat for Type.

11. Press OK.

Figure 18: New Shapefile Layer window

12. This will open the Save layer as… window.

13. Save the file in the folder Hirst Wood Shapefiles as 1847 Ordnance Survey

Six-Inch England and Wales.

14. A new layer should now appear in the Layers Panel

called 1893 1-2500 First County Series Survey.

15. We now need to add information to our Polygon

Vector Data layer. To do this select the 1893 1-

2500 First County Series Survey in the Layers

Panel and click on the Toggle editing icon (right).



16. Now click the Add Feature icon to begin.

17. This will activate a small crosshairs cursor on the map window. We will begin

by zooming in on the site of New Hirst Mill (southwest corner of Hirst Wood)

and mark the outline of the large mill structure (Figure 19). To do this hover

the crosshairs over one corner of the building and left click.

18. This will place a vertex onto the location. As you move the cursor a thin red

line will connect the cursor with the first vertex. Following the line of the

wall in either a clockwise or anti-clockwise direction and click on the

next corner to place another vertex. Repeat the process until all of the

corners are marked and right click.

19. This will open a Feature Attributes window. In the box Site Name write New

Hirst Mill (Disused). In the box Type, write Structure. Press OK.

20.

21.

Figure 19: Polygon of New Hirst Mill created

Now repeat the process for other features recorded on the map. Only complete the

Site Name box in the Feature Attributes window if the polygon created has a name

(like New Hirst Mill, Mill Race, Weir or Hirst Wood).

We don’t tend to create polygons for trackways and roads as these will stand out

once the surrounding polygons have been created. The polygon Types we use are:

Water

Structure



Woodland

Field

Quarry

Rough Pasture

Moorland

Recreation Ground

20. When complete, press the Save Layer Edits icon to save your work and select

Toggle Editing icon to come out of editing mode.

21. As with point vector data, you can change the way they appear by going into

Layer Properties (See below for example).



3.0 Using Raster Data

What is Raster Data?

In its simplest form, a raster consists of a matrix of cells (or pixels) organized into

rows and columns (or a grid) where each cell contains a value representing

information, such as temperature. Rasters are digital aerial photographs, imagery

from satellites, digital pictures, or even scanned maps.

A common use of raster data in a GIS is as a background display for other feature

layers. For example, orthophotographs (photographs that are geometrically

corrected) displayed underneath other layers provide the map user with confidence

that map layers are spatially aligned and represent real objects, as well as additional

information.

Rasters are well suited for representing data that changes continuously across a

landscape (surface elevation). They provide an effective method of storing the

continuity as a surface. They also provide a regularly spaced representation of

surfaces. Elevation values measured from the earth's surface are the most common

application of surface maps, but other values, such as rainfall, temperature,

concentration, and population density, can also define surfaces that can be spatially

analysed.

In archaeology we display Light Detection and Ranging (LiDAR) data as Rasters.

3.1 Importing Raster Data

We will now import vertical aerial orthophotographs available from the Environment

Agency. This data can serve as a basemap, as well as a way to check the accuracy

of the vector data

On the saved Hirst Wood project click the Add Raster Layer icon (figure 16). This

will open the Open a GDAL Supported Raster Data Source window.

Figure 16



Search for the Environment Agency folder in the GIS Workshop Data and open the

folder labelled Ortho-RGB-15CM-2007-SE13nw and select and Open the four files

listed.

Figure 17: Don’t forget, as it is hiding all of the vector data, you may want to move the raster

aerial photograph layer to the bottom in the Layer Panel.

You will now be able to view the vertical aerial photograph data for Hirst Wood

(figure 17) and its surroundings. To make this data more manageable, select each

of the files labelled:

Ortho_P00011338_20070310_20070404_1m_res

Ortho_P00011284_20070310_20070404_1m_res

Ortho_P00011271_20070310_20070404_1m_res

Ortho_P00011270_20070310_20070404_1m_res

Right click, and select Group Selected on the drop down menu. To rename the

group, right click on the group title and select Rename from the drop down menu.

Press Save.



3.2 Georeferenced Raster Data

Raster files such as aerial photographs or images of historic maps can be imported

into QGIS and georeferenced so that they can analysed alongside other raster data

(such as LiDAR) and vector data (such as survey point data).

We will attempt to georeference the PDF map Yorkshire 201 1842-52 Ordnance

Survey Six-Inch England and Wales (copyright National Library of Scotland) using

the vertical aerial photograph layers imported previously.

1. From the horizontal toolbar select Raster and then Georeferencer.

2. This will open the georeferencer window (figure 18).

Figure 18: Georeferencer window. The raster logo on the left of the horizontal toolbar will

open a browser window to open up your raster image.

3. Click on the Open Raster icon to search and load the map/image to be

georeferenced. Select and open the PDF Yorkshire 201 1842-52 Ordnance

Survey Six-Inch England and Wales.

4. Once the image is loaded, check the settings found along the menu toolbar at

the top of the Georeferencer Window. From the dropdown menu select

Transformation Settings.

5. In the Transformation Settings window check Transformation type is set to

Polynomial 1; Target SRS is EPSG:27700 OSGB 1936/British National Grid.



6. Select Output Raster and ensure the File Name is: Yorkshire 201 1842-52

Ordnance Survey Six-Inch England and Wales_modified and press Save.

7. Ensure the box Load in QGIS when done is ticked.

8. Press OK (figure 19).

9. To begin select the Add Point Icon.

10. This will activate a crosshair cursor which you will use to select a location on

the imported map which matches a location on the aerial photographs. The

best places to selects are the corners of fields or corners of buildings; as well

as the ends of bridges.

11. First select a location on the Dowley Gap Aqueduct at the western end of

Hirst Wood. I have selected the point where the eastern bank of the River

Aire meets the southern edge of the aqueduct, as this is unlikely to have

altered significantly.

12. You will then be prompted to confirm the co-ordinates by a Enter Map Co-

ordinates window. As we do not know the co-ordinates we will match the

location with our aerial photograph. Select the From Map Canvas tab (figure

19).

Figure 19: Once a point on the Raster image is selected click the From Map Canvas tab in

the Enter Map Co-ordinates window.

13. You will then be returned to the main map window where you can select the

same location on the aerial photograph. Try to be as accurate as possible



with your selection, as any significant spatial differences between the two

points will lead to a poorly georeferenced historic map.

14. When you select the location and left click you will be returned to the

Georeferencer window and Enter Map Co-ordinates window where you can

press OK to confirm the selection.

15. Repeat the process for at least four more locations, making sure to select

locations around the area of Hirst Wood.

16. When complete select Start Georeferencing from the File dropdown menu.

17. After a short period of time the imported map image will be imported as a

georeferenced image in the main map window. Close the Georeferencer

Window and when prompted save the GCP points (the points selected for

georeferencing).

On completion the georeferenced historic map should look something like this

(above). You can alter the transparency of the historic map layer from the Layer

Panel.



4.0 Using Light Detection and Ranging (LiDAR)

What is LiDAR?

‘Airborne lidar (light detection and ranging) measures the height of the ground

surface and other features in large areas of landscape with a very high resolution

and accuracy. Such information was previously unavailable, except through labour-

intensive field survey or photogrammetry.

It provides highly detailed and accurate models of the land surface at metre and sub-

metre resolution. This provides archaeologists with the capability to recognise and

record otherwise hard to detect features.

Airborne LiDAR operates by using a pulsed laser beam fired from a plane. The beam

is most commonly scanned from side to side as the aircraft flies over the survey

area. It measures between 20,000 to 100,000 points per second to build an

accurate, high resolution model of the ground and the features upon it’ (Historic

England, 2017).

Figure 20: Principals of LiDAR (Holden, 2002).

LiDAR produced by the Environment Agency can be downloaded from the

Government’s Open Survey Data webpage in two forms.

Digital Surface Model (DSM)

A DSM is a model of the surface of the earth that includes all the features on it such

as vegetation, buildings, cars etc.




Digital Terrain Model (DTM)

A DTM is a ‘bare-earth’ model in which mathematical algorithms have been used to

remove features such as vegetation and buildings (Great for identifying woodland

archaeology).

Depending on availability LiDAR DSM and DTM files can be downloaded at 0.25m,

0.50m, 1m or 2m resolution. The higher the resolution (i.e. 0.25m) the clearer the

data and the more likely very subtle features will be identified across the landscape.

Recognising Archaeological Features

Here are some examples of archaeological features identifiable using LiDAR.

Routes of Communication

Terraced tracks and holloways are some of the easiest features to identify (below).

They are often linear and link one area of activity with another.

Quarries

Mineral extraction sites (quarries) take on many forms. From small shallow delves or

pits (below left) to large cuts exposing bedrock (below right).

Platforms

Platforms are either raised or terraced level surfaces. Platforms may have

supported structures, temporary accommodation, working/storage areas or

alternatively (depending on shape and size) may indicate locations of charcoal

production.



Walls

Relict field boundaries or woodland boundaries can also be identified by means of

LiDAR.

4.1 Importing LiDAR Data

When downloaded, LiDAR data is in the format of an ASCII (American Standard

Code for Information Interchange) file. In order to use these QGIS needs to convert

them into a Raster format (Thankfully QGIS does this automatically).

Before you begin, it is good practice to organise your folders to ensure all of your

data does not get muddled up or lost! First open your folder GIS Workshop Data,

right click and select New Folder. Rename it LiDAR Merge. We will use this folder

to house our various LiDAR files.

Open your Hirst Wood project to begin importing the LiDAR tiles:

1. Select the Add Raster Layer icon

2. Go to GIS Workshop Data, Environment Agency, LiDAR 1m DTM and select

the four files: se1237_DTM_50cm.asc, se1238_DTM_50cm.asc,

se1337_DTM_50cm.asc, se1338_DTM_50cm.asc and press Open.

3. The LiDAR DTM tiles should now visible on your map window (figure 21). If

they are not, it probably means they have been imported using the wrong

Coordinate Reference System. To correct this right click on each DTM tile

listed in your Layers Panel and select Set Layer CRS from the drop down

menu. In the Coordinate Reference System Selector window change the

CRS to OSGB 1936 / British National Grid EPSG: 27700 and press OK.



Figure 21: Imported LiDAR DTM tiles.

4. We now need to merge the four tiles into a single tile so that we can start to

analyse the data. From the tool bar above the map window open Raster and

from the drop down menu select Miscellaneous and then Merge (figure 22).

5. In the Merge window, where it reads Input Files, search for the four DTM

files. In the Output File select your newly created LiDAR Merge folder and

type Hirst Wood DTM 50cm Merge and press OK (figure 23).

6. The process may take a while and can

sometimes crash! If it does, switch off the

underlying layers and try again.

7. When complete, click Close on the Merge

window.

8. The merged LiDAR DTM tile should now be

visible on your map window (figure 24).

If it is not, it probably means it has been

imported using the wrong Coordinate

Reference System. To correct this right click

on the Hirst Wood DTM 50cm layer listed in

your Layers Panel and select Set Layer CRS

from the drop down menu. In the Coordinate

Reference System Selector window change

the CRS to OSGB 1936 / British National

Grid EPSG: 27700 and press OK.

9. Press Save.

Figure 22:



Figure 23: Merge Window

Figure 24: Map Window displaying the merged DTM tiles Hirst Wood DTM 50cm Merge



4.2 Slope Modelling

Analysing LiDAR as a slope model, in essence calculates the slope severity for each

of the cells which form the individual tiles. The visualisation of slope as part of our

woodland surveys across the South Pennines is particularly useful as many of the

woodlands are located on often steep valley slopes. This type of analysis is great at

identifying features cut into these slopes such as trackways, platforms and quarries.

It is less successful in the identification of more subtle features such as ridge and

furrow and sometimes boundaries.

To create a Slope Model with our merged LiDAR data:

1. From the tool bar select Raster, Terrain Analysis and Slope.

2. In the Slope window (figure 25), make sure the Elevation Layer is Hirst Wood

DTM 50cm Merge. For Output Layer select the folder LiDAR Merge and

type Hirst Wood DTM 50cm Slope and press Save.

3. Then press OK.

4. After a few moments is should load up, but you may have to change the CRS

again (See below).

Figure 25

5. Using the icon drag a square over the area of Hirst Wood to zoom in

(figure 26).



Figure 26: Slope DTM Model of Hirst Wood. You should be able to see the individual

trackways, quarries, platforms and boundaries within the woodland. The lighter colour

represents slope whereas the dark colour represents a flat or gently undulating surface.

6. You can reverse these colours by right clicking on the layer in the Layers

Panel and selecting Properties and then Style in the Layer Properties

window. Change the Colour Gradient to White to Black in the drop down

menu and press OK (figure 27).

Figure 27: Reversing the colour may make features within the woodland easier to see.



4.3 Hillshade Modelling

Hillshade analysis is the most common algorithm applied to LiDAR data. Each cell is

given a shading value based upon a hypothetical light source. Relief is directly

illuminated which makes it possible to recognise features. It is particularly effective

for earthworks and subtle features such as ridge and furrow or largely ploughed out

features. However, as it utilises a hypothetical light source, multiple algorithms will

need to be applied in order to obtain a more complete understanding of a feature or

landscape.

To create a Hillshade Model with our merged LiDAR data:

1. From the tool bar select Raster, Terrain Analysis and Hillshade.

2. In the Hillshade window (figure 28), make sure

the Elevation Layer is set to Hirst Wood DTM

50cm Merge.

3. In Output layer select the LiDAR Merge folder,

type Hirst Wood DTM 50cm Hillshade 300 40

and press Save.

4. The Illumination stats represent the direction

from where the light source emanates

(Azimuth) with 0 or 360 representing north.

The Vertical Angle represents the height of

the light source. These are the stats you can

change in subsequent analysis. I always add

these stats to the file title as a reminder.

5. Press OK.

Figure 28: Hillshade Window

Figure 29: Hillshade DTM of the merged Hirst Wood files.



5.0 Creating and Saving a Map

Having loaded up some of our data we now want to create a map. This can be a bit

awkward, but practice makes perfect. Remaining in the map window, reorganise

your layers so that your Raster layers are at the bottom and your Vector Layers are

on top.

You may want to switch off your vector layers or alternatively change the way they

appear. It is possible to change the transparency of a layer by opening up its

Properties and selecting Style (figure 30).

Figure 30: Here I have opened up the properties for the SE_Woodland layer and set the

Layer Transparency to 90.

The Hirst Wood

map window

once I have

played with the

settings of each

layer.



To create a map for publication you will need to access the Print Composer.

1. Select the New Print Composer Icon from the top menu bar.

2. Type Hirst Wood in the Composer Title window and press OK.

This will open a map window titled Hirst Wood (figure 31).

Figure 31: Map window

3. Select the Add new map icon from the top menu bar.

4. Place your cursor at a corner of the map page and then left click to mark a

rectangle before releasing. This will import the map to the page (figure 32).



We will now start to add core information to the map.

5.1 North Arrow

1. Select the Add Arrow Icon from the top menu bar.

2. Place your cursor over the map, left click and drag the mouse to draw a

line, when ready release.

3. To change the line width or arrow size you can use the Arrow Properties

window on the right hand side of the map window (figure 33 below).

5.2 Scale Bar

1. Select the Add New Scalebar Icon from the top menu bar.

2. Using your mouse, left click on the map and the scale bar should

automatically appear in metres.

3. To change the style of the scale bar access the Item Properties listed on the

right hand side of the map window (figure 34 below).



5.3 Legend

1. Select the Add New Legend Icon from the top menu bar.

2. Left click on the, map window where you would like it to appear.

3. You can control what appears in your Legend using the Item Properties listed

on the right hand side of the map window. To do this you need to make sure

the Auto Update box is not activated

(figure 35).

4. You can then use the icons to add

or remove items from the Legend box.

Figure 35:

5. You can also change the name of each

layer by highlighting a layer and clicking the

icon . Type the new name in the window

and press OK.

On completion you map window should look something like this:



5.4 Text Box

Adding a text box is important for making reference to the material displayed in the

map. This map contains Ordnance Survey and Environment Agency data.

1. Using the GIS ACKNOWLEDGEMENT Word Document, Copy the

acknowledgements for the OS Open Data and Environment Agency.

2. Click on the Add New Label Icon located in the top menu bar.

3. Paste the text from the GIS ACKNOWLEDGEMT Word Document into the

Label Main Properties menu on the right hand side of the map window

(figure 36).

4. The text will automatically load into the New

Label box on the map. However you may

need to change the size of the box using

your cursor in order to see all of the text.

Figure 36:

5. The text may be difficult to read as the box is

transparent. To change this, scroll down the

Label Main Properties until you find

Background, and click on the box. This will

provide your label with a white background.

5.5 Save Map

When you are happy with your map, select Composer from the top menu bar and

select Save Project from the drop down menu. This will save the map window as a

template for any further mapping you wish to carry out.

To save the map for publication and printing select Composer and select either

Export as Image or Export as PDF from the drop down menu.

Celebrating Our Woodland Heritage QGIS 2.18.14 Manual · 1 Celebrating Our Woodland Heritage: QGIS...

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