Google Earth allows for the viewing of 2D or
3D colour satellite imagery for any point on the Earth, as well as being able
to view galaxies and the ocean floors. The surface terrain imagery can usually
be viewed at a scale in the region of 1:2500 without any loss of detail
quality. This figure can vary from region to region, but it is generally true
for built up areas.
Google Earth, therefore, makes a vary useful
visual display tool for SURPAC Users when it is interfaced, or linked, with survey
co-ordinate and/or image data. This interfacing can be in the form of :-
Displaying the locations of Trig. Beacons and/or Town Survey Marks for a selected area.
Displaying Beacons and Stations from a previous survey to help locate these points.
Displaying User selected Points in a Co-ordinate file to help locate these points.
Displaying Points and/or Lines from a survey plan, or sheet, to view their positions.
Displaying a survey Plan, or Sheet, itself as an overlay image on the earth surface, etc.
Importing a Placemark created in Google Earth into SURPAC.
Importing a Line, Path or Polygon created in Google Earth into SURPAC.
Importing a Google Earth Image into SURPAC.
Requirements
to enable SURPAC interfacing with Google Earth
1.
Google Earth must be installed on the computer. If you do not
already have Google Earth
installed, visit http://earth.google.com/ and follow the on-screen
instructions for installing this software. The basic version of Google Earth is free and is quite suitable
for the SURPAC
interface functions discussed below. There is the option of the Google Earth Pro version, but at a cost of US$400
(about R2,500).
2.
The currently loaded Co-ordinate file in SURPAC must use either the WGS 84 ellipsoid, the GRS80 ellipsoid or any other ellipsoid
having the same parameters as the WGS 84 ellipsoid.
3.
A reasonably fast ADSL or 3G wireless internet connection.
Optional
Setting the Google Earth Display of SURPAC Data and Overlays
1. The SURPAC data displayed on Google Earth does not always provide an exact
visual fit on to the satellite imagery. In order to force the displayed data to
fit as close as possible to the imagery, you can use the Google Earth Ruler tool to determine the Y, X (or E, N) shifts to be applied to the SURPAC data, or image, so that it best
fits the imagery.
2. A plan, or sheet, that is
displayed on Google Earth as an
overlay can have varying levels of transparency applied to it. Increasing an
overlay’s transparency allows more of the imagery lying under the overlay to
become visible. Setting a zero transparency will allow the overlay to
completely hide the underlying imagery. Note
that on Google Earth itself there is a “slide” option
(on the Sidebar information display) that allows for further refinement of the overlay’s
transparency level.
3. An overlay of a plan, or sheet,
may also be viewed whereby the sheet background is completely transparent,
i.e. only the detail on the sheet, such as the lines, text, hatching etc. will
be displayed. For this option to apply, the sheet background colour has to be
white, which is the case for all SURPAC CAD sheets.
4. Line information sent from
SURPAC
to Google
Earth
can have the following options :-
Users can set the Lines to be sent
using their defined Line Thickness values.
Users can set the Lines to be sent using their defined Line Colour values.
If Lines are to be sent using a Single Colour, then this colour can be User
defined.
All SURPAC CAD programmes which use the Google Earth display function have a menu
item whereby the Google Earth display
option can be set or viewed. The options may also be set by clicking the [File
options] button when in the “Co-ordinate
File Editing”
programme.
Displaying
the “Locate and Add Nearest Trig/
1. In SURPAC run the Locate
and Add Nearest Trig/
2. Set the search options at the
bottom of the form so as to display the required number and type of beacons.
3. From the displayed list of
beacons, remove any unwanted beacons by clicking on the green tic shown at the end
of each display line. The green tic will change to a red cross. This point will
remain “dormant” and will not be displayed until clicked again.
4. Click on the [View
List on Google Earth] button at the bottom right of the form.
SURPAC will open and run Google Earth and the selected beacons will be
displayed at their surface positions on the satellite imagery. Either a Trig. Beacon or a
The
Beacon Name
The
The
Co-ordinate System (e.g. WG29°)
The
Beacon Y, X and Z values (or E, N and H values)
The
Beacon Latitude and Longitude
Example of a 3D View of Trig Beacons
displayed on Google Earth
Displaying
selected Points from the Co-ordinate File on Google Earth
1. In SURPAC, run the
Co-ordinate File Editing programme from the General main menu heading.
2. Mark (i.e. highlight) the Points
required for viewing on Google Earth.
2.1 You can mark a block of Points by either clicking on the first Point in the block and then dragging the
cursor onto the last Point, or by clicking on the first Point in the block then
holding down the Shift key and simultaneously clicking on the last Point in the block.
2.2 You can mark
individual Points by clicking on the first
required Point and then, whilst holding down the Ctrl key, click on any other
required Points.
2.3 You can mark
Points by Description by clicking on the [File Options] button and then selecting the Select Points to be Highlighted (by Description) option. Then select the required Descriptions from the displayed list.
3. After selection, Click the [Export GE KML] button on the Actions Bar menu.
The Points selected will be
displayed at their surface positions on the satellite imagery by Google Earth. Either a Point, a Trig. Beacon or a
The Point
Name
The Point
Description
The
Co-ordinate System (e.g. WG29°)
The
Beacon Y, X and Z values (or E, N and H values)
The
Beacon Latitude and Longitude
Interfacing
SURPAC CAD programmes with Google Earth
These functions apply to the General CAD, Contour CAD, General Plan CAD, Sectional Title CAD and Working Plan CAD
programmes.
Note that the Contour CAD
programme only has the Viewing a SURPAC CAD Sheet on Google Earth option available.
Viewing
a SURPAC CAD Sheet’s Lines and Points on Google Earth
Note :-
Before
proceeding, view and/or reset the Google Earth options in SURPAC (see
above).
If the Point Display option
is On, then only
the Points that have been Named (by using the [PN] Command)
will be displayed on the Google Earth overlay.
All Lines will be shown in the User selected style, width and
colour. Refer to Paragraph 4 of “Optional Settings” on Page 1.
All
Points will be marked by either the SURPAC Point
marker or, in the case of Trig. Beacons and TSMs, the appropriate control point
symbol.
1. In the CAD
programme, click on the “File” main
menu heading and then select the View Lines and Points on Google Earth menu item. (Note :- If the Point Display has been turned Off, then
this menu item will read View Lines on
Google Earth).
2. Once the CAD
sheet Line and Point data have been transferred, Google Earth will shift its location to the centre of the
imagery covered by the data and will display the data viewed from an
appropriate height. The Orientation
is set to North and there is no Tilt applied.
All viewing settings can be User modified from within Google Earth. Clicking on a displayed Point will show a text
balloon containing the Point’s values and information.
.
Example of a new township layout, showing Lines and
Named Points, on Google Earth
Viewing
a SURPAC CAD Sheet on Google Earth
Notes :-
Before
proceeding, view and/or reset the Google Earth options (see above).
One
problem associated with using a CAD Sheet as
an overlay is that of the Meridian Convergence. Since a CAD Sheet is always oriented to Grid North (the True North at the
Central Meridian of the projection) and not to True North at the Sheet position, SURPAC has to swing the CAD Sheet
display so as to re-orient it to True North.
Before
the image of a CAD Sheet is
sent to Google Earth as an overlay, you will notice it being re-drawn in
SURPAC. This is
to both re-orient the Sheet for Meridian Convergence, as explained above, and to set
the Sheet scale to the defined plotting scale. This latter action is too ensure
a clearer Sheet image on Google Earth. For the Windows Vista operating system (which has better graphic memory
handling), the scale is set to half the defined plotting scale to provide an
even clearer overlay image.
1. In the CAD
programme, click on the File main
menu heading and then select the View Sheet on Google Earth menu item.
2. Once the CAD sheet has been transferred, Google Earth will
shift its location to the centre of the imagery covered by the Sheet and will
display the Sheet viewed from an appropriate height.
Notes :-
The Sheet Orientation is set to True North (regardless of the
Sheet Swing used) and there is no Tilt applied. All view settings can be User modified from within Google Earth.
The Sheet overlay will be “locked” to the
terrain covered by the Sheet. Hence, when viewed in 3D, the Sheet will drape itself over the
terrain, much like a table cloth laid over a piece of rocky ground. If the
Sheet background has been set as fully transparent (see Google Earth Options), then
only the Sheet data, such as Lines, Text, Hatching etc. will be shown. Otherwise,
the Slide on the Google Earth Sidebar can be
used to change the Sheet overlay transparency.
Example
of a SURPAC Township layout Sheet, with partial transparency, on Google Earth
Example
of a layout with full background transparency, on Google Earth
Example of a 3D semi-transparent CAD Sheet
Overlay, plus Trigs on Google Earth
Transferring a Google Earth Placemark position to a SURPAC
Co-ordinate File.
Creating a Placemark in Google Earth
In Google Earth, ensure that either the Toolbar or the Sidebar
are displayed. Move the Google Earth display to show the required
area at the required scale.
To create a Placemark, click
the appropriate toolbar icon, or select the "Placemark" menu
item found under the "Add" menu heading. The new Placemark
Dialog Box appears and the cursor changes to a flashing, square
drawing tool. Enter the properties for the
Placemark and give it an appropriate Name. Since SURPAC
will use the Placemark Name as the name for the imported Point,
use a SURPAC friendly name, i.e. up to 8 characters in length.
Move the cursor onto the flashing
drawing tool, and then drag the tool to the required screen position, by
holding down the Mouse LHB as the cursor is moved. Once the drawing tool is
correctly positioned, click the [OK] button on the dialog box. The newly
created Placemark will be added to My Places. (Warning,
if you have a
The created Placemark now needs to be saved as a
On the displayed Save file … form, ensure that the Save
as Type item is set to
Importing the Placemark into a SURPAC
Co-ordinate File as a Point
Before attempting to import the Placemark data into a
Co-ordinate file, first ensure that the file System is set to
either the WGS 84 or GRS80 ellipsoids and that the Central
Meridian of the WG System, or Zone, is correct for the Point data to be
imported.
In the SURPAC Co-ordinate File Editing programme, click on the [Import
GE
From the displayed File Selection form, select
the
Transferring a Google Earth Path, Line or Polygon to a SURPAC
General CAD Sheet
Creating a Path or Polygon in Google Earth
In Google Earth, ensure that either the Toolbar or Sidebar
are displayed. Move the Google Earth display to show the required
area at the required scale.
A Path may be a single Line,
or a series of connected Lines. To create a Polygon, click the
appropriate toolbar icon, or select either the Path or the Polygon
menu item found under the Add menu heading. The new Path or new Polygon
Dialog Box appears and the cursor changes to a square drawing
tool. Enter the properties for your drawing and give the Path or Polygon
an appropriate Name. You can change the style and/or colour for the line
or polygon from the default white to better visualize the shape you are about
to draw. You can also enter an appropriate Name for the Path or Polygon
to be created.
Click in the viewer to start the
drawing creation and use the following method to achieve the desired shape :-
Regular shape - Click and release method. Move the Mouse to
a new point and click to add additional points. In this mode, the cursor
remains a square drawing tool whilst the Path or Polygon being
drawn is displayed up to the last clicked position. Polygons will
automatically be closed back onto the defined starting position. Whilst
drawing, the last clicked position can be deleted by clicking the Mouse
Once construction of the Path or Polygon is complete,
click the [OK] button on the dialogue box. The Path or Polygon
created will be added to My Places. (Warning, if you have a
The created Path or Polygon information now needs to be
saved as a
On the displayed Save file … form, ensure that the Save
as Type item is set to
Importing the Path or Polygon into a SURPAC
General CAD Sheet
In the SURPAC General CAD programme first set the required Pen
Style, Colour and Thickness to be used for the imported
lines. Click on the File menu heading and then select the Import
Lines from Google Earth
NB : The same importation method can be used to import Line information from a SURPAC (and compatible) generated
Transferring a Google Earth Image to a SURPAC General CAD Sheet
Creating an Image Bounding diagonal Line (Path)
and defining an Image in Google Earth
In Google Earth, ensure that the Toolbar and Sidebar
(found in the Layers Panel) are displayed. Move the Google
Earth display to show the required area at the required scale.
Click the Google Earth “Tools” menu heading and select Options….
Select the 3D View tag and then set the Show
Terrain option to OFF. (This is important. If Google
Earth is viewed using the Terrain option as ON, images become
distorted due to terrain height variations.)
Use the Navigation Control (displayed at the top right
corner of the Google Earth display) to set the orientation to True
North (click the N symbol at the top of the Navigation Control).
(This is also important. If Google
Earth is not viewed in True North orientation, the image
will be distorted when sent to SURPAC.)
Tips
In order to be able to select the full image displayed,
click on the Google Earth View menu
and ensure that the Status Bar is not displayed.
To maximise the image area, click on the Google Earth View menu and
ensure that the Sidebar is not
displayed.
With the Google Earth image
oriented to True North and the Terrain option
turned off, create
a Path (as described above) consisting of a single line, by carefully
clicking on the top left and then the bottom right corners of the Google
Earth display area.
Save this Path as a
NB : After creating and saving this Path,
it is important that the Google Earth display is not changed
in any way until the current image has been saved.
Click on Google Earth’s File menu heading, then
select the Save menu item and then the Save Image sub-menu
item. In the Save As dialogue box, enter an appropriate file Name.
The file type is automatically set to the Jpeg format. Save the file in the
same folder as the associated Polygon (normally the C:\Surpac_GE folder).
NB : The Google Earth Pro
application is able to create image files at a higher resolution than the
standard Google Earth. However, the Pro version is not
free and costs about US$400.
Importing the Google Earth Image to a SURPAC
General CAD Sheet
In the SURPAC General CAD programme ensure that the sheet size
and scale are correct for the Image to be imported. Then import the Image
bounding diagonal line via the Path
On the CAD Sheet, locate the
cursor at the approximate centre of the Polygon, then click the Mouse
NB : This last setting is important
as it is necessary for SURPAC to apply a small rotation to the incoming Image
to compensate for Meridian Convergence. This due to the Google
Earth Image being oriented to True North and the SURPAC
Image being oriented to the Grid North (i.e. the True North at
the central meridian).
The Sheet will automatically be re-oriented by the amount of the
Meridian Convergence. On the SURPAC General CAD Sheet,
move the cursor to the top left terminal of the imported Path (or Line) and then click the Mouse
LHB. Now move the cursor to the bottom right terminal of the imported Path
and then click the Mouse
SURPAC will now apply a swing to the Image to correct for
the Meridian Convergence. The Sheet will again re-orientate back to 0° and
display the adjusted imported Image.
NB : The Image may not fit exactly onto the Path
terminals, due to the former having been swung to compensate for the
Adjusting the Imported Sheet Image
Setting the Image to the Background – If the Image
lies on top of existing Line and Text items then set the Image as the background, i.e. the Lines, Text, Points etc. will be
displayed on top of the Image. To do this, right Click on the Image,
click the Image menu heading and then select the menu item Send
Images to the Back.
Shifting the Image - The imported Image
may need to be shifted in the Y and/or X directions to get a good
fit with any existing Sheet data. If this is required, right Click on the Image,
click the Image menu heading and then select the Shift a Sheet Image
menu option. On the displayed form, enter the Y and/or X movement
required for the Image. This option can be repeated to ensure a good
fit.
Adjusting the Image Brightness and/or Contrast – Images required
for background information may need their brightness and/or contrast adjusted
to avoid the Images interfering with the display of Lines and Text. To
do this, right Click on the Image, click the Image menu heading
and then select either of the Adjust Image Brightness or the Adjust
Image Contrast menu options. On the displayed form, use the slide bars to
set the required brightness and contrast values.
These
SURPAC Google Earth functions
make use of the importation of height data interpolated via the Google Earth Elevation API. This
function allows for the interpolation of heights of locations anywhere on the Google Earth DTM.
Summary
Based
on tests carried out on data samples in areas in
Applications
Generating
Contour and DTM files via downloaded Google
Earth data provides rapid and useful
data that have various small scale applications. When displayed in conjunction
with an imported Google Earth image, these become even more
useful. The generated Contour and DTM files can also be exported as KML files for client viewing directly
on Google Earth itself. Examples of useful applications are for :-
·
Township planning
approval
·
Sub-divisional
planning approval
·
Preliminary
water/gas/fuel pipe alignment over long distances
·
Preliminary
road/rail alignment over long distances
·
Cross section data
for preliminary mass haul calculations
·
Preliminary dam
site investigations (water volume versus wall height etc.)
1.
Co-ordinate File Editing Programme
1.1 Import Points from a KML file – This existing function has been extended so as to allow
the import of multiple Points contained in a KML file, and not just a single Point as was the case previously.
1.2 Importing interpolated
1.3
Compare Existing heights with interpolated
Using this Option
:
If you want to restrict the comparison of Google Earth heights to selected Points, then first highlight these Points
in the Co-ordinate file listing as explained above. Then, in the Actions Menu, click on the [File Options] menu item to display
the File Options form. Click on Compare File and Google Earth Heights and then click on the [OK] button. If you have highlighted a set of Points, you will be
prompted if you want to restrict the height importation to these Points. Reply
as appropriate.
A form will be displayed in which the selected Points,
their co-ordinates, description, surveyed heights and interpolated Google Earth heights will be shown. These height comparisons are imported
at a rate of approximately 350-500 Point heights per minute, depending on your
internet connection. Statistical data relating to the comparison of heights are
shown at the bottom of the form.
There is also an option whereby you can compare Google Earth heights for a single, User selected Point.
Using this Option
:
In the Co-ordinate file display, right click on the
Point whose height you want to compare. On the “pop up” menu that will now be
displayed, select the menu item Compare
Height with Google Earth. A form will then be displayed showing the Point
selected, its co-ordinates and height, the Google
Earth height and the difference.
Moving the cursor away from this form will cause it to be removed.
1.
Tacheometric File Editing Programme
The
main and most important function regarding the importation of Google Earth 3D data is the generation of Tacheometric files, using data solely imported via Google Earth interpolation, as explained below.
2.1 Import Points with interpolated
Using this Option
:
In the Actions
Menu, click on the [Import GE Data]
menu item. The form below will be displayed, allowing you to enter the four
points used to define the required quadrilateral. The named Points should exist
in the current Coordinate file, otherwise their co-ordinates must be entered
manually.
To ensure that the quadrilateral covers the correct area,
these 4 Points are best determined by using Google Earth to create Placemarks at the appropriate
positions. The quadrilateral does not have to be square, nor does it need to be
oriented NS or EW. Any four Points that enclose the required area are sufficient.
One restriction is that, when entering
the 4 Points into the above form, they must be entered in a clockwise sequence,
normally starting at the Point that is approximately the NW corner.
SURPAC will then proceed to calculate Tacheometric file points
along the perimeter lines of the quadrilateral, as well as on all Grid
intersections lying within the quadrilateral, using the defined Grid interval.
Once all points are calculated, their heights are interpolated from Google Earth and all point data are added to the file. These Tacheometric
points are imported at a rate of approximately 350-500 Points per minute,
depending on your internet connection.
SURPAC Contour CAD, showing imported Google Earth Points on a
50m Grid
This generated Tacheometric
file can then be used in the SURPAC Contouring CAD programme to construct and edit contour lines (using the
Triangulation method) over the quadrilateral area, in the usual way.
The two preceding images and the one on the next page show
the stages of generating a contour display from imported Google Earth points,
i.e. defining an area, importing the data, creating the Contours and then
displaying these contours on Google Earth via a KML file.
SURPAC 5m Contours of Hartebeespoort dam wall area using
Google Earth Data
2.2
Compare Existing heights with interpolated
This function is useful when needing to evaluate the
accuracy of imported
Using this Option
:
In the Actions
Menu, click on the [Compare GE Hts].
A form will be displayed in which the file Points, their co-ordinates,
description surveyed heights and interpolated Google Earth heights
will be shown. These height importations are imported at a rate of
approximately 350-500 Point heights per minute, depending on your internet
connection. Statistical data relating to the comparison of heights are shown at
the bottom of the form.
3.
Contour Generating CAD Programme
3.1 Compare
existing heights with interpolated
Using this Option
:
3.1.1 Comparing a
Single Point
Right click on the Spot
Height that is to be compared and then, from the
3.1.2 Comparing
the entire file
Click on the
3.2 View 3D Contours
& DTM on Google Earth – Once all the
contours have been generated and edited, using the Surface Triangulation
method, you can view the contours alone, or the contours and the solid 3D model
created from the surface triangulation in situ on the Google Earth surface.
Using this Option
:
Click on the File
main menu heading and then select View
Contours & DTM on Google Earth menu option.
On the displayed form, first read the help information by
clicking on the [?] icons, to see
the implications and use of the available options, especially with regard to
the two Surface Options. These options allow for the display to be “clamped to the Google Earth “ surface, or to have it shown as a free standing 3D model.
The former method would be used for Contours that represent the natural earth
surface and the latter for both Contours and DTMs of manmade features such as
stockpiles, dumps and earthworks.
NB : Google Earth will not display any
imported KML data that lie below its
own surface. Trying to display an
excavation, for example, is not possible if the excavation Contours and DTM lie
below the natural surface.
SURPAC 3D Triangulation Model and Contours displayed
in situ on Google Earth
In the
above example, the “Show Display in 3D over the Google Earth Surface” was used.
This mode is necessary for physical manmade features, such as dumps or
stockpiles, that overlay the pre-existing natural surface.
SURPAC 3DTriangulation Model and Contours of a slimes dam survey, viewed
in situ on Google Earth
Summary on displaying 3D Models in Google Earth
In Google Earth it is
possible to view imported and superimposed KML
data from various view ports. This can be done dynamically using the Mouse, as
follows :-
·
Panning – Hold down the Mouse Left Hand
button and move the cursor in the desired direction.
·
Scaling – Scroll the mouse scroll wheel
forwards or backwards.
·
3D Object Viewing – Move the cursor to the centre of
the object, then hold down the Mouse Middle button. Moving the cursor forwards
or backwards will change the Tilt (vertical) view point. Moving the cursor left
or right will change the Orientation (horizontal) view point. The amount of vertical height exaggeration
can be set in Google Earth by clicking on the Tools menu and selecting the Options… menu item.
The
following image of
Google Earth will
only allow the downloading of 2,500 “locations” per user per day. As SURPAC collects data at a rate of 4 points
per location, this maximum daily limit is increased to 10,000 points. For areas
that require more than this limit, separate the area into two or more sections
and download the data on consecutive days (or just use a different e-mail
addresses if you have them!)
SURPAC 20m Contours of Table Mountain using Google Earth interpolated Data
4.
Longitudinal Sectioning Programme
A new
function has been added that allows for the generation of Longitudinal Sections
by the direct importation of interpolated
Using this Option :
Click
on the [Set File Type] menu item in
the Actions Bar menu. On the
displayed form, select the “Section
Plotting Using a LONG-SECTION File only” option and Click the [OK] button.
Click
on the [Select a File] menu item in
the Actions Bar menu. From the
displayed form, enter the new File Name and Click on the [Open] button.
Once
the “Long Section Creation/Editing”
form is displayed, Click on the [Options]
button. From the displayed list, select the “Generate Sections from defined Bend Points and
A form
will then be displayed that allows you to enter the Bend Points that define
the
Required
Long. Section. These Points must exist in the current Co-ordinate File.
NB : An easy way
to import a series of Bend Points is to define a Path in Google Earth that
follows the required route. This Path
can then be imported into the SURPAC
General CAD programme. After this, use the option that Converts Line terminals into Points. The [Y, X] values of these Points
will then be stored in the Co-ordinate File. Finally, use the Co-ordinate
File’s “Import interpolated
Once
all Bend Points have been entered, select the required Interpolation Interval
for the section and then Click the [Proceed]
button.
A SURPAC Long Section through Lion’s Head,