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Click here to return to course outline.
A GIS geological mapping project involves five stages: 1) the georegistration of existing topographic base maps, geological maps, aerial photographs, radarsat and satellite images, and geophysical data images, to a common grid reference system; 2) the separation of the various classes of existing spatial information onto a set of georegistered layers; 3) preliminary analysis of the resulting data set; 4) ground-truthing and further data collection in the field; and 5) final organisation of layers and analysis of the data.
Layering
involves the separation of data into classes in the form of georeferenced
layers. For example, the recently published data for an area
of northern Manitoba known geologically as the Flin
Flon - Snow Lake Belt (approx 250km E-W and 150km N-S) is
broken down into the following layers:
Landsat TM imagery for a 1:250k sheet - all seven
bands
Synthetic Aperture Radar (SAR) data - both airborne
and satellite for selected areas
bedrock geology maps
geological field observations, including lithological,
structural, and mineral observations
surficial geology map
quaternary data sets (clay geochem, grain size,
carbonate content striae, etc.)
digital hydrography
geophysical imagery (gravity, aeromagnetics (total
field and vertical gradient))
radiometric imagery
mineral occurrence data
geochronological data
In the case of Field course 350Y, for example, the inital stage of a GIS compilation for the Coniston region of Sudbury would involve georegistration of:
the 1:20,000 digital basemap for Coniston,
the relevant part of geological map 2491,
the airphoto coverage for Coniston,
the relevant aeromagnetic image,
the relevant landsat images
This would be followed by the separation of the geological information (bedding and foliation orientation, faults, rock units, etc) on geological map 2491, and analysis of the aerial photographs and remote sensed images in an attempt to, for example, predict faults, joint patterns, bedding or foliation trends, and the presence of dikes, contact metamorphic zones, or argillized zones, etc.
When in the field, the predictions of the preliminary analysis can be 'ground truthed', and new data added to the spatial data base (e.g. measured dips and strikes; rock unit boundaries; sample locations, etc). Finally, with all the data assembled, the interpretive addition of rock unit boundaries and the generation of a topology and a polygon map may be attempted. The following image shows 'road' (red lines), 'railway track' (green lines), 'shoreline' (blue lines), 'town-site boundary', 'map 2491 geological boundary' (black and cyan lines), 'map 2491 bedding trend' (magenta lines) and 'bedding strike and dip symbol' layers in the Coniston/Garson region superimposed on a georegistered false-colour satellite image and two aerial photographs of part of the region. In this module we will attempt to carry out the first three stages in preparation for the 350y field course. But first we need to understand something about map projections.
Which Map is Best? - Projections for World Maps, 1986, 14 p., Special Publication
No. 1, Committee on Map Projections of the American Cartographic Association
(ISBN 0-9613459-1-8). (Not in Library)
Choosing a World Map -
Attributes, Distortions, Classes, Aspects, 1988, 15 p., Special Publication
No. 2, Committee on Map Projections of the American Cartographic Association
(ISBN 0-9613459-2-6).
Matching the Map Projection
to the Need, 1991, 30 p., Special Publication No. 3, Committee on Map Projections
of the American Cartographic Association (OSBN 09613459-5-0).
Snyder, J.P. 1984, Map
Projections used by the U.S. Geological Survey, Washington: U.S. Geological
Survey Bulletion 1532, 313p. (Call # US1 IN2 82B32; TAY govt 28 day).
Peter Richardus and Ron.
K. Adler, 1972, Map projections for geodesists, cartographers and
geographers. North-Holland Pub. Co., Amsterdam. ( Call #
GA110.R52, DBW stack 28DAY)
Snyder, P.J., 1984, Map
Projections - A working manual. US Geological Survey Professional Paper.
US Dpt. of the Interior 1395,100 p. (Call # US1 IN47 84P95
TAY govt 28DAY; US1 IN47 84P95 DBW govt 14DAY)
Geodesy
is concerned with the area and shape of the Earth, and in particular the
definition of a reference Earth shape known as the Geoid.
The Geoid is
an equipotential surface of gravity, ellipsoidal (oblate spheroid) in shape
because of the counter-gravity centrifugal forces generated by the spin
of the Earth about its N-S axis, and highly irregular because of the variability
in composition (density) of the Earth beneath each point on the Geoid (note:
these irregularities are not necessarily coincident with those exhibited by the Earth's
surface). The ellipsoid
model of the Earth attempts to define its shape in terms of a smooth ellipsoid,
and the use of satellite measurements have led to the development of the
WGS-84 (World Geodectic System) ellipsoid as the best ellipsoidal representation
of the Geoid. The maximum difference between the Geoid and the WGS-84 ellipsoid
is 1 in 100,000 (c. 50-100 metres). Ellipsoids have also been constructed
for individual continents and countries because different ellipsoids give
better fits to the Geoid at different locations, e.g. the Clarke 1866 ellipsoid
for the United States.
The
Geoid and Ellipsoid
The Ellipsoid information, an initial location
(origin), an initial azimuth (the direction of north), and the distance
between the Geoid and the Ellipsoid at the initial location defines a permanent
reference surface known as a 'Datum'. For example, the NAD-27 datum
(North American Datum , 1927 ) is based on the latitude and longitude of
Red Falls, Iowa, whereas the WGS-84 ( World Datum, 1984) is based on measurements
made from space, beyond the effects of local variations in gravity. Each
datum embodies its own concept of latitude and longitude, and at
any given locality, changing the datum may change a coordinate reading
by several hundred metres; in the Sudbury region the difference in UTM
latitude between NAD-27 and NAD-83 is 223 metres. When giving a coordinate
location it is therefore always necessary to also give the datum being
used.
Geodetic (geographic) coordinates are given in
terms of latitudinal degrees measured relative to the equator and and longitudinal
degrees measured relative to either east or west of the prime meridian
running through Greenwich, England.
Kinds of Map Projection
Map projections involve the transformation of a 3-dimensional form into a 2-dimensional plane; they record the curved surface of the Earth on a flat display. They may be cylindrical, conical or azimuthal (planar).
Cylindrical
and Conical Map Projections
As illustrated in the previous linked figure, a cylindrical projection can be realized by wrapping a sheet of paper around the globe, in the form of a cylinder, projecting the geographical features onto the paper, and then unrolling the paper as a flat sheet. Note that the great circle of contact with the cylinder is the equator, and that the lines of latitude and longitude projected along normals to the cylinder will draw as an orthogonal graticule (grid) with the lines of longitude equally spaced but the lines of latitude unequally spaced. Although the shape of a large area is distorted, small areas are displayed relatively accurately . The maps are said to be conformal.
A conical
projection is generated in the same way but with the paper wrapped
as a cone such that the conical surface intersects the globe as a tangential
line of latitude, or, more usually, passes
shallowly through the globe between two small circles or latitudes
known as standard parallels (the secant case).
Standard
parallels. Lines of latitude and longitude would
in this case appear on the flattened sheet as a fan-shaped graticule, and
all features lying on the concentric circles of intersection would be undistorted.
The most common conical projection is the Lambert
Conformal Conic Projection.
Lambert
Projection
Map projections inevitably introduce distortions of direction, area and shape into a map, and the projection to be selected depends upon the requirements of the mapper. No map projection can offer a uniform map scale, and projected polygonal features may retain either their area or shape, but not both. The properties of various projections are listed in the following link: Map Projection Properties, Mapping Suitability, and Uses
MAP PROJECTION SPECIFICATIONS FOR LAMBERT CONFORMAL - OGS Data set 12
The Township and Areas were digitized from hardcopy 1:50,000 scale NTS maps and assembled into an Ontario-wide fabric in Lambert Conic Conformal map projection. The following parameters define the planimetric reference grid:
Clarke 1866 ellipsoid a=6, 378,206.4 (equatorial radius) e=0.006768658 (eccentricity squared)
Standard parallels 49 degrees N latitude 77 degrees N latitude
Origin 92 degrees W longitude 0 degrees N latitude; Central Meridian 92 degrees W longitude
False Easting 1,000,000 metres
The Central Meridian at 92 degrees runs N-S just west of Atikoken, Rainy River; the western limit of the area has an easting of 750 km and the eastern limit an easting of 2500 km; the false easting origin lies approximately at the longitude of Duluth.
MAP PROJECTION SPECIFICATIONS FOR LAMBERT CONFORMAL - GSC, Geological Map of Canada
Lambert Conformal Conical Projection parameters
Type
Lambert Conformal Conic projection
Datum
North American Datum 1927 (NAD27)
Units
metres
Spheroid
Clarke, 1866
Lambert
standard parallels
49 00 00 N
77 00 00 N
Projection origin
95 00 00 W (central meridian)
49 00 00 N
False origin
(easting, northing)=(0, 0)
The Universal Transverse Mercator System (UTM) employs a transverse cylindrical method of projection such that distorsion is minimized along a given line of longitude, and a plane orthogonal (rectangular) coordinate system. The Earth is divided into 60 UTM zones each of 6 degrees of longitude, the zones being numbered from west to east, starting a 180W. Sudbury is located close to the centre of zone 17. The line of longitude at the centre of each zone represents Grid North, and coincides with True North. The N-S lines of the UTM coordinate grid (Eastings) are drawn parallel to Grid North, whereas the E-W lines of the grid (Northings) are drawn parallel to the Equator. The intersection of Grid North with the Equator (the true origin of the zone) is arbitrarily given a coordinate location of 500000 metres East and 0 meters North, such that a false origin for the grid, that is the point where the numbering sytem is 0 in both axes, is located 500 km west of the true origin. Note that the closer one gets to the zone boundary the larger the angular difference between True North and the UTM N-S grid line. Consequently when plotting dips and strikes of beds measured relative to Magnetic North, it is necessary to correct for this difference. At Sudbury the difference is only about 10 seconds, and therefore the correction can be disregarded.
LINKS
COORDINATE CONVERSION SOFTWARE
http://mac.usgs.gov/mac/isb/pubs/pubslists/fctsht.html
http://www.ngs.noaa.gov/PC_PROD/pc_prod.shtml#UTMS
http://everest.hunter.cuny.edu/mp/software.html
http://users.skynet.be/tandt/
http://cousin.stud.uni-karlsruhe.de/kkisbin/trafo.tcl
[In the following notes, '->' mean 'select the following option in the previously designated menu', e.g. Draw -> Point means select the Draw menu in the toolbar at the top of the screen and then the Point menu in the presented drop-down list.]
Setting
up a Cad-based mapping project involves five main steps:
1) creating a virtual coordinate grid for the area to be studied.
2) a) scanning and attaching a basemap, and registering the basemap to the
virtual grid;
or b) attaching an existing digital map tile.
3) making the basemap transparent if not a digital tile.
4) scanning the aerial photograph to be attached to the coverage.
5) attaching, and registering aerial photographic coverage to
the basemaps.
6) scanning, attaching, resampling any existing geological maps.
In the following procedure we will carry out only operations 1), 2b) and (5. To follow the full procedure go to:
http://instruct.uwo.ca/earth-sci/505/350proj.htm
Image
File Size
An aerial photograph is about 9 inches by 9 inches size, and scanned at
a resolution of 600 dpi the photograph is composed of about 29 million
pixels representing a .tif file size of about 27 Mb. If viewed in
Microsoft Photoeditor the image size is about 5100 x 5400 pixels.
If this image is saved as a greyscale .jpg image at 80% quality the file
size will be reduced to 5.5 Mb. Such an image can be zoomed to about 400%
before excessive pixelation takes place. After gamma corection the file
size can be reduced to about 3.2 Mb. The resolution will be sufficient
to resolve a car on the highway, but not the driver. It should be possible
therefore to identify an outcrop a few square metres in size.
Files
On
the D: drive of your computer, create a directory D:\MyFiles\'yourinitials'\Fieldlog\'yourinitialsconiston',
where 'yourinitials'
really means your initials, e.g. wrc.
Via My Network Places -> Entire Network -> Microsoft Windows Network -> Gp -> Earthsci -> Public go to Public\Es350\fieldlog\350digbasemaps\5105140coniston on the departmental server, and copy the file 5105140nad83.dwg (this is the digital base map for the Coniston region of Sudbury) to the folder 'yourinitialsconiston' that you have just created on your computer. Similarly, copy the airphoto image 4620-122.jpg and the map image 2491falconbridge.jpg from Public\Es350\fieldlog\coniston.
Quick course in Autocad
The instructor will explain the following drawing operations/functions in AutoCad Map: 'window zoom', 'transparent zoom', POINT, PL, coordinate location, the layer window, MAP, TRANSFORM, RUBBERSHEET, ALIAS, ATTACH, LOCK, FREEZE, DIST, TEXT, BPOLY, ADEFILLPOLYG.
NOTE: in Autocad any operation can be cancelled by pressing the ESC key.
Creating a reference UTM grid
1) Using a paper base map, estimate the maximum UTM coordinates of the boundaries of the airphoto to the nearest kilometre e.g. top left 509000 metres, 5149000 and bottom right 514000 metres, 5145000 - record these values on a piece of paper.
2) Load Autocad Map and start a new project.
3) Assign NAD 83 as the UTM projection for the relevant zone by following the sequence of steps Map -> Map Tools -> 'Assign Global Coordinate System' -> Codes. In the scroll-down 'Categories' box, scroll to and select 'UTM-NAD83', and in the 'Available Global Coordinate Systems' scroll-down box select NAD83 UTM Zone 17 North, Meter. Click OK and note that the Current Work Session has been assigned the coordinate system code of UTM83-17. Click OK once again to complete the operation.
'Save As' your drawing file as 'yourinitialsconiston'.dwg in:
D: \My files\'yourinitials'\Fieldlog\'yourinitialsconiston'.
4)
Click the 'Paper Layer' icon (icon representing by a set of separated white
layers) in the tool bar. The Layer
and Line Type Property Window will appear. Click the
New button, enter the name '4620-122airphoto'
in the name box. Repeat these instructions to make a set of layers named 'Author', 'Coordgrid',
'Coordgridnames', and 'Coordpoints'. Click the
'Current ' button to make this last layer (Coordpoints)
the current layer. Exit the Layer Manager.
5) From the toolbar
select Draw
->
Point -> 'Single
Point' and type in a coordinate
location representing one of the UTM kilometer grid intersection points,
e.g. 509000, 5149000 (= top left).
To make the points visible, click 'Format'
on the Toobar ->
Points -> select
a point symbol, and click OK. Enter 'Regen'
at the command line to regenerate the drawing.
Repeat the requisite number of times to create a
500 metre point grid for the area
covered by the aerial photograph - top left 509000, 5149000 and bottom right 514000,
5145000.
6) Get the Layer and Line type
Property Window and, click the 'Coordgrid' layer and make it the current layer.
Exit from the Layer manager, and toggle OSNAP on by double
clicking the OSNAP button in the toolbar at the bottom of the screen. Use
the 'Polyline'
line drawing tool (the command line shortcut is 'pl')
to draw lines connecting the coordinate points.
7) Make the layer 'Coordgridnames'
the current layer,
and enter the X or Y coordinate of each line in the line grid (ordinate
values to the left and the abscissa values along the bottom) by clicking
Draw
-> Text -> click the position to place the
annotation, give a text height of 100, a rotation value of '0', and then type in the
coordinate. Press the ENTER key twice. Repeat for each line in the grid.
8) Make the layer 'Author' current and add your name in the bottom right corner of the grid.
Now make a final check that the coordinate points have the correct values - turn on tje OSNAP function and move the cursor to the coordinate point. The coordinate value will be given in the tool bar box at the bottom left of the screen.
SAVE YOUR FILE
Attaching a Digital base map
Four ODBM tiles:
5005140nad83 (Ramsey Lake, lower left coordinates
500000, 5140000)
5005150nad83 (north Sudbury, 500000, 5150000);
5105140nad83 (Coniston, 510000, 5140000),
5105150nad83 (Garson Mine, 510000,5150000),
have been corrected, converted to NAD83, and archived
in (Public):\350\fieldlog\350digbasemaps.
To attach the 5105140nad83
digital database - which you have already copied to your computer - to the current project, select select
MAP -> Drawing -> Define Drawing Set; the 'Define/Modify Drawing
Set' window will appear.
The
'Define/Attach drawing file' window and the 'Select Drawings to attach'
window
Click Attach to bring up the 'Select Drawing
to Attach' window.
If an alias has not been defined, click the 'Create/Edit
Aliases' button (fourth button from the right) to fetch the 'Drive Alias
Administration' window. Provide the drive alias name 'My Files' in the requisite box,
and define the path in the 'Drive Alias Details' box (use BROWSE to define
the path D: \My Files) --> click Add followed by Close.
Alias Page
Select the alias name in the Drive
Alias box in the 'Select Drawing to Attach' window, and click-select to your
directory 'yourinitialsconiston'. A list of .DWG files
in the directory will appear in the File
Name selection box. Click 5105150nad83, followed by ADD, and then click OK
twice.
To plot the
information in the base map to the screen, make the selection
sequence:
Map -> Query -> 'Define query'.
Query
window
Click 'Property', then the Layers button
followed by the Values button. In the drop-down selection list hold down
the CTRL key and select the following layers:
Rail_Line, River_Stream, Road_Centreline,
Shoreline, Trail, and Transmission line. Click OK twice.
Location
Condition window
Click the DRAW button in the Query Mode box ->
and the Execute Query button. Finally, carry out a 'Zoom (z) Extents (e)' to display
the image.
SAVE YOUR FILE
Attaching the scanned airphoto
To Attach the scanned airphoto to the Autocad .dwg drawing file, first make the relevant layer (e.g. 4620-122airphoto) current (see The Layer and Line Type Property Window). Secondly, estimate approximately the coordinates of the lower left corner of the image, and, finally, carry out the operation Insert (on the Toolbar) -> 'Raster Image'. In the Raster Image window click the Attach button, then in the resultant 'Attach Image' window click the Browse button and in the 'Attach Image File' window select the image you wish to insert. Click the Open button. This will return you to the 'Attach Image' window. In the Image Parameters section, enter a rough estimate of the location of the bottom left hand corner of the airphoto in the 'At:' data entry box, click the 'Specify on Screen' button for the Scale Factor, specify the rotation angle as '0', and then click OK. A rectangle representing the relative dimensions of the image will appear on screen. Within the rectangle will be a rubber band which when dragged will redefine the dimensions of the rectangle. Drag the rubber band to create a rectangle that approximates the area of the photo as estimated from the plotted locations, and click the left mouse button to terminate.
Alternatively you can carry out the operation :
Map
-> Image -> Insert ->
In the 'Image Insert' window select the file to attach and click the OPEN
button.
In
the subsequent INSERT window,
click the Pick
button. A cursor in the form of a +
will appear on the screen with a small rectangle in the top right segment
of the +. Click the the lower left corner
of the rectangle already drawn to represent the airphot (the rectangle
on layer '4620-122Photoboundary', and drag the cursor up and to the left to enlarge
the rectangle to approximately the size of the image being attached. Click
the left mouse button followed by either the right mouse button or the
ENTER key. Click the OK button in the Insert
window that should now have reappeared on the screen. At this stage the
placement of the image does not have to be accurate. Use Tools
-> 'Display Order' -> 'Send
to back' to place the image layer behind the location layer.
Moving the airphoto (digitized map) to its correct coordinate location (Transform)
The airphoto (digitized map) can be placed in its correct coordinate position using the 'Transform' operation in Autocad. This involves selecting two points on the airphoto that can be matched with two points on the reference base map.
Create a new layer called '4620-122Transformpoints', make it the current layer, insert the two points (points, ENTER, click on point) to be used as the transform reference points (the points to be matched on the airphoto), and LOCK the layer. This constitutes a record of the points used in the transformation of the airphoto.
Follow the operational sequence Map->'Map Tools' -> 'Transform'. When requested to 'Select/Layer' the object to transform, key in 's' ENTER and click on the edge of the airphoto. Press Enter to terminate the selection.
[Note: To zoom into location points while selecting points on the base map and airphoto, enter 'z (apostrophe z) and window an area around the points. Do a 'z, p sequence to zoom back out to extents, and a 'z w to zoom back down to the next base point, etc, etc.]
In response to the request 'First source point', zoom down to the source point on the airphoto, click on the source point, turn OSNAP on (double click the OSNAP button on the bottom toolbar), and in response to 'First Destination Point', click on the corresponding point on the reference base map . Repeat for a second source and destination point. The image will know be transformed to its georegistered location.
Carry out the operation Tools -> Display Order -> Send to back, so that the photo forms a backdrop to the base map. Examine carefully the relative location of objects such as roads, railway lines, drainage, etc, on the base map and the airphoto, and note any obvious discrepancies. Distances can be measured by entering 'DIST' ENTER as a command, and clicking the end points of the length to be measured. The distance will appear on the bar at the bottom of the screen.
SAVE YOUR FILE
Rubber Sheeting the airphoto
Airphotos are usually distorted, with the distortion least in the centre of the photo and greatest at the edges. To some extent the distortion can be accounted for by carrying out a 'Rubber Sheeting' operation.
Using the Rubber Sheet facility of Autocad Map, a known set of UTM grid locations on the scanned base map will be calibrated with the same points on the airphoto. Note, the first point entered will be the coordinate locality on the image, the second point will be the corresponding locality on the location layer. [It is also possible to attach a georegistered Spot, Landsat, or Radarsat (8 meter resolution) image to the drawing project, and use this image as a template to rubber sheet the airphotos.] When rubber sheeting, freeze all objects that do not need to be reoriented. Also, lock (but do not freeze) the layer containing the location points that you are going to use as reference points, otherwise they may be moved by acident as part of the rubber sheeting reorientation.
First create three new layers - 4620-122refpoints,
4620-122prerubb, and 4620-122postrubb, each with a different coulour.
Make the layer 4620-122refpoints the current layer,
and create a set of points corresponding to locations on the base map that you
can also easily recognise on the airphoto. Lock this layer.
Make the layer 4620-122prerubb current and create
on it the points on the airphoto that correspond to the reference points you
have just selected on the base map. Lock this layer also. If only these two layers are turned on, the degree of distortion of
the airphoto relative to the base map can be easily visualized.
To carry out the rubber sheet operation, first
make the layer 4620-122postrubb the current layer, toggle OSNAP Off by
double clicking the OSNAP
button on the tool bar at the bottom of the screen, and then run the sequence:
Map->'Map
Tools' -> 'Rubber
Sheet'. On the command line Autocad
will request that you input 'Base Point 1'. To zoom into the location
points while carrying out the rubber banding, enter
'z (apostrophe z) and window the area around the base point and
the reference location. Then click on the base point on the photograph,
turn OSNAP on, and then click the reference point. Do a 'z,
p sequence to zoom back out to extents, and a 'z
w to zoom down to the next base point, etc, etc. When you have finished
adding base points and are zoomed out, press the ENTER key. Choose the
Select option by entering 's' on the command line, press ENTER, and click
the edge of the image. The image will change shape according to the reference
data entered during the rubber sheeting.
Record on the layer 4620-122postrubb the new locations of the reference points on the airphoto. The effect of the rubbersheeting can be gauged by an examination of the relative postion of the reference points on the 4620-122refpoints, 4620-122prerubb, and 4620-122postrubb layers.
SAVE YOUR FILE
Inserting a scanned geologic map
To insert the geological map
2491falconbridge.jpg, carry out the same procedure as for
the airphoto but exclude the rubber sheeting operation. Use
the operation 'Tools -> Display Order -> Send to
back' to place the geological map behind all other drawing objects.
Data
Layering
Once the base maps, airphotos and geological maps
have been registered, geological information can then be redrawn on their own
specific layers, e.g. :
Alines 2491 geological boundaries copied from map 2491 of the Sudbury region
2491Beds bedding
orientations taken from map Sudbury map 2491
2491Beds_trendlines lines
representing generalized bedding trends
2491Fol
foliation orientations taken from map 2491
2491Fol_trendlines lines representing generalized foliation trends
2491faults faults taken from map 2491
2491Geolbruce polygons
delineating the distribution of the Bruce Formation
2491Geolbrucefil colour filled polygons for the Bruce Formation
2491Geolgabbro2491 polygons for the Nipissing diabase
2491Geolgabbro2491fil colour filled
polygons for the Nipissing Gabbro bodies
2491Geolpecors2491 polygons for the Pecors Fm
2491Geolpecors2491fil colour
filled polygons for the Pecors Fm.
2491Geolsuddiab2491 polygons for the Sudbury diabase
2491Geolsuddiab2491fil colour filled
polygons for the Sudbury diabase bodies
2491GeolMiss249 polygons for the Mississagi Fm
2491GeolMiss249fil colour filled polygons for the Mississagi Fm.
ETC
Studentsstati stati localities
visited by students during ground truthing
Studentsstruct
bedding orientation measured by students
Studentsfol
foliation orientation measured by students
Studbruce
distribution of rocks of the Bruce Fm
Studbrucefil
filled polygons representing the Bruce Fm
ETC
Use the Autocad SKETCH or PL (polyline) functions to 'heads-up' copy geological boundaries and faults, etc, to their corresponding layers.
To create and colour-fill geological map units copied from digitized maps you will need to request instruction in the use of the Autocad BPOLY and ADEFILLPOLYG functions.
Drawing
in Autocad - http://instruct.uwo.ca/earth-sci/505/draw1.htm
Drawing
using the Fieldlog Database - http://instruct.uwo.ca/earth-sci/505/draw2.htm
Calibrating
the tablet - http://instruct.uwo.ca/earth-sci/505/draw3.htm
(If the objects you are
going to digitize are on maps of different scales, see:
http://instruct.uwo.ca/earth-sci/505/draw3.htm#IMPORTANT1
SAVE YOUR FILE.
Make a directory path Fieldlog\'yourinitialsconiston'\ in your area in 'USERS'
on the departmental server, and copy
all files used or created in this exercise to this directory.
Plotting
Select the The Layer and Line Type Property Window and turn off all layers except the 'author', 'coordgrid', and '4620-122airphoto' layers. Window the area you would like to output.
Click
File -> Print.
In the 'Plot/Configuration' window note that
the 'Window' button in 'Additional Parameters' has been selected.
Click the MM button in 'Paper Size and orientation',
and in the 'Scale, Rotation and Origin' box enter 50 for 'Plotted MM' and
1000 for 'Drawing units', where '50' means millimetres and '1000' means
metres; make sure the 'Scaled to Fit' box is deselected (no tick);
In the 'Plot Preview' box click the Full button
and then click 'Preview'; a view of the image on the page should appear;
if the image is as it should be click ESc to return to the 'Plot/Configuration'
window, and click OK to print.
Collect your print in room 17 and give to Professor
Church for laminating.
Volo View Express
Volo View Express is a free Autocad program that you can down-load to your personal computer, and which allows you to view the layers in Autocad .DWG files, and to add a layer containing lines (straight lines and polyline sketch lines) and annotated text. The program can be used most usefully in three ways. Firstly, to zoom to enlarged parts of the photograph, thereby facilitating preliminary 'airphoto interpretation', secondly, to obtain the UTM coordinates of locations on the photograph, and thirdly, to draw bedding/foliation/lineament trend-line maps prior to carrying out 'ground truthing' in the field.
The Volo View Express set-up file ' vve2setup.exe ' can be downloaded to your computer from:
http://instruct.uwo.ca/earth-sci/fieldlog/Volo_View_Express/
Volo View Express has also been loaded onto all the computers in room 17.
TIPS
In Tools -> Options -> General: select 'Revert to Pointer' in the 'After using Drawing Tool' preference box.
In Tools -> Options -> 'File Locations' -> 'Folders to search for support files and xrefs:' enter the path to the directory containing the airphotograph and base-map images, e.g. the path to the .dwg files in your area in USERS.
To draw a straight line - a) click the sketch button on the toolbar; b) place your cursor on the start location of the line on the photograph and click once; c) move the cursor as small a distance as you possibly can; d) click a second time; e) drag the green node that will appear on the screen to the end location of the line; f) the line can be move by dragging the end nodes of the line (if there are more than two nodes in the line, simply superimpose two of the nodes).
Printing multiple copies of Autocad images on the HP Colour PS printer
Set the printing option in Autocad to Default printer and in Printers select the default printer as the HP Colour PS printer (mail room).
Print the Autocad plot file to file.
Change file extension from .plt to .prn
Load the file into Ghostview, select Postscript as the print method, and indicate the numbers of copies to be printed.
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