Freezing and lockinglayers
 Entities on frozen layers are ignored when regenerating, and are not displayed or plotted. Freeze layers that are not of immediate interest, this will speed up editing, zooming and panning. Layers that are merely turned off are regenerated during a REGEN command. A thaw command must also be followed by a REGEN.
 Entities are still visible on a locked layer but cannot be edited. It can however be made current and new objects can be drawn. The locked entities can be used in Snap mode, and one can change a locked layers colour and linetype. It can also be turned off and frozen. Freeze is therefore a more definitive command than Lock.

 When creating topology, points, lines and polygonal lines must be on separate layers.
 To turn all but one layer off or turn all layers on or move objects from one layer to another (Layer Match) use Bonus -> Layers on the Toolbar.

***********************************************************************************

 Exercise 1 - Creating topology and polygons without using BPOLY

 IF you have carried out the exercise involving the import of the data sets 200AV3.txt and 200BV3.txt into a Fieldlog database, plot a map showing statype symbol and the lithcode.
 IF you have not imported these files, read the following but carry out Exercise 2 below.

 Make a layer called Boundary (FORMAT -> Layer -> New), make it the current layer, and draw a rectangular map boundary around the plotted data using the 'rectangle' drawing tool in the drawing Toolbar.
 Similarly, create a Layer called Lines, and a set of layers corresponding to the geological rock types granite, diabase, limestone, sandstone. Make the Lines layer the current layer.
 Using the polyline drawing tool (PL - command line), draw the granite polygon on the current Lines layer (NOT the granite layer).
Draw boundaries for diabase, limestone, and sandstone units, but dot not try to end the lines accurately at the intersecting boundary. Rather, extend the lines slightly beyond the intersecting boundary, e.g. extend the diabase boundary line with the sandstone slightly beyond both the intersecting  rectangle and granite boundaries. Determine the approximate maximum distance of the extensions (referred to as dangles) using the 'DIST' command described above.
Freeze the layers related to the point data generated by Fieldlog. Only the drawn boundary lines (polylines) should be visible in the drawing.

 Clean up the polygon boundaries
Select Map -> Map Tools -> Map Cleanup.
 In Object selection, click the Select Automatically button.
 In Object Selection click the Delete Original and Create New Objects button.
 Click the Create on original and the Line to Polyline buttons.
In Clean Up Options  select all 7 dissolve options, and set the Tolerance to a value greater than the length of the longest 'dangle' to be removed. Click OK and the Proceed button.

 To create a topology for the cleaned objects.
 Proceed with Map -> Topology -> Create.
 Provide a Name for the topology e.g. grantop, select polygon as Type of Object, and  Link Objects.
 On the Link Objects menu, click the Select Manually and select all the lines defining the granite polygon. Click OK. [NOTE: if the centroid is to be created on the current layer, make sure the 'Create Missing Centroids' button in the Polygon Options selection box has been checked, and click the Proceed button. A centroid will be placed automatically within the polygon.]
 Click the Centroid objects button and in the Create on Layer Box type the layer name as grantop. [NOTE: if a point or other object, e.g. text, already exists within the polygon, it is possible at this point to select the object as the centroid, rather than having the centroid automatically created.]
 Click the OK button, make sure the 'Create Missing Centroids' button in the Polygon Options selection box has been checked, and then click the Proceed button.
 Repeat the process for other geological units, creating diabtop, limetop, and sandtop topological layers.
 Proceed to the paragraph on the following page, entitled 'To examine the topological data attached to the centroids'.

Exercise 2

 1) Create LINE, FAULT, POLYTOP, and GRANITE layers.
 2) Make the LINE layer current.
 2) Draw a NW-SE diagonal line to represent a fault boundary.
 4) Starting a very small distance east of the fault line draw a boundary polyline to represent the western component of a faulted granite body, ending the line a small distance east of the fault line. Repeat this procedure to draw the eastern component of the faulted granite body.
 5) Measure the approximate maximum length of the dangling objects (the dangling lines of the granite boundaries).
 6) Clean up the boundaries via Map -> Map Tools -> Map Cleanup.
 In Object selection, click the Select Automatically and the Delete Original and Create New Objects buttons.
 Click the Create on original and the Line to Polyline buttons.
In Clean Up Options select all 7 dissolve options, and set the Tolerance to a value greater than the length of the longest 'dangle' to be removed. Click OK and the Proceed button.
 7) Use MODIFY to move the fault line segments extending beyond the granite components to the FAULT layer, and freeze this layer.
 8) Select Map -> Topology -> Create.
 Provide a Name for the topology e.g. polytop, select polygon as Type of Object, and  Link Objects.
 On the Link Objects menu, click the Select Manually and select all the lines defining the granite polygon (could also select automatic). Click OK.  [NOTE: if the centroid is to be created on the current layer, make sure the 'Create Missing Centroids' button in the Polygon Options selection box has been checked, and click the Proceed button. A centroid will be placed automatically within the polygon.]
 Click the Centroid objects button and in the Create on Layer Box type the layer name as polytop. [NOTE: if a point or other object, e.g. text, already exists within the polygon, it is possible at this point to select the object as the centroid, rather than having the centroid automatically created.]
 Click the OK button, make sure the 'Create Missing Centroids' button in the Polygon Options selection box has been checked, and then click the Proceed button.
 To examine the topological data attached to the centroids
To view the topological data attached to a centroid, select Map -> Object Data -> Edit Object data -> click the object. The data includes an ID number, the area and perimeter length of the polygon, and the number of lines (links) composing the polygon.

 To create a Polygon layer from the Topology layer
 Select Map -> Map Tools -> Create Closed Polylines.
  Provide a name for the topology, e.g. grantop or polytop, and for the layer on which to create the polygons, e.g. granite (you earlier created this layer).
 You will now have a layer with the cleaned line data (Lines), layers with topological data (centroids) for each rock type e.g. grantop or polytop, and polygon layers for each geological unit, e.g. granite.
 If a granite object is subsequently drawn and added to the topology, all the granite objects on the 'polygon' granite layer should be erased and then recreated with the 'Create Closed Polylines' procedure.
 If the apparent polygons are topological polygons composed of polyline assemblages with centroids, operations that change the properties of the centroid. e.g. colour or layer, etc, also change the properties of the polylines. If the polylines are blue and located on a blue layer, and the centroid is changed to a red colour, the polylines will also change to red rather than remain the colour of the layer on which they reside.

 To attach object data to drawing objects
 1) To define an object data table, select Map -> Object Data -> Define Object Data -> click 'New Table' -> supply a Table Name eg. Rock_unit -> in Field Definition supply a Field name, e.g. rock_type, a description, and default value -> in the 'Type' box select 'Character' as field type -> click Add -> repeat to add e.g. a 'Mineralization' and 'Age' field -> click OK -> click CLOSE in the Define Object window.
2) To attach data to an object, select Map -> Object Data -> Attach/Detach Object Data -> select the object table in the Table box -> click the desired field in the 'Object Data Field' box, e.g. rock_type, and type in the entry for that field, e.g. granite -> press ENTER -> repeat for the other fields -> click 'Attach to Objects' -> click the object to which the data is to be attached and then press ENTER to end the operation.
3) To view the data attached to an object, select Map -> Object Data -> Edit Object data -> and click the object.