Inserting New Points

The Insert option from the Points Menu allows you to create new points in a variety of ways.  When selected, the dialog box shown below is displayed.  

The Insertion Method group defines the calculation method for the plan position of the new points.  Each method requires you to indicate different reference data.

The Height Calculation group defines the calculation method for the height of any new points.  Some of these methods are not valid for all insertion methods.

The Parameters group displays the basic data for inserting new points.  The Point Code field displays the code that will be assigned to new points.  The default values in the drop down are the available code prefixes and underneath is a text string which displays the description of the current code prefix.  The Start Point Number defines point number of the first new point, subsequent point numbers being incremented.  The Prefix Created Points check will enable you to add a point number prefix of I to each new point.  The Add to List check allows you to add all new points to the point list.

Calculating the Location of New Points

The Sketched method will insert points based on the current position of the mouse cursor.  Each time you click on the left button of the mouse, a new point will be created.  You can use the Lock Mode setting to ensure that points are placed in locations coincident with anything displayed in the backcloths, for instance, the ends of lines or corners of buildings.  For this method, the Relative and Linear Interpolation height calculations are not available.

The Relative XY method allows you to insert a series of points relative to an existing reference point.  You will be asked to indicate the reference point and then use a dialog box to enter the offsets, as shown below.  Each time you select the OK button, a new point will be created and the dialog box will be redisplayed using the previously entered offsets as the defaults.  For this method, the Linear Interpolation height calculation is not available.

The New XY method allows you to create a series of new points by typing known co-ordinates.  A dialog box, like that above, will be displayed allowing you enter a series of new point co-ordinates.  Each time you select the OK button, a new point is created and the dialog box will be redisplayed with the previously entered co-ordinates being used as the default values.  For this method, the Relative and Linear Interpolation height calculations are not available.

The Angle & Distance method allows you to create a series of points by entering an angle and a distance.  Firstly, you will be asked to indicate two points which form a reference line.  You will then be asked to enter a series of angles and distances using a simple dialog box.  The angle is the angle from the reference line to the new point and the angle convention is that clockwise from the reference line is positive.  The angle should be entered in the angle units set in the current defaults.  The distance is the plan distance between the new point and the first point of the reference line.  The Relative height method will calculate heights based on the first reference point.  The Linear Interpolation height method will calculate heights based upon a linear interpolation of the entered distance along the reference line.

The Bearing & Distance method allows you to create a series of points by entering a bearing and a distance.  Firstly, you will be asked to indicate a single reference point from which all calculations will take place.  You will then be asked to enter a series of bearings and distances using a simple dialog box.  The bearings should be entered in the angle units set in the current defaults.   The distance is the plan distance of the new point from the reference point.  The Relative height method will calculate heights based on the reference point.  For this method, the Linear Interpolation height method is not available.

The Distance Along method allows you to create a series of points that are at known distances along a reference line.  Firstly, you will be asked to indicate the two points which form the reference line.  You will then be asked to enter a series of distances using a simple dialog box.  The distances entered should be that from the first point on the indicated reference line.  For this option, the Plan Chainage check box becomes visible but will only be enabled if the Linear Interpolation height method is set.  If checked, the distance you enter will be assumed to be the plan distance to the new point.  If it is not checked, the distance will be assumed to be the slope distance to the new point.  The Relative height method will calculate heights based on the first point and the Linear Interpolation height method will interpolate along the indicate reference line.

The Points Along method allows you to add a fixed number of points between to reference points.   You will be asked to indicate the start and end of the reference line and then enter the number of points to be created using a simple dialog.  Only the Linear Interpolation height method will be available for this insertion method.

The Chain & Offset method allows you to calculate the position of points that are a known distance along and a known perpendicular offset from a reference line.  Firstly, you will be asked to indicate the two points which form the reference line.  You will then be asked to enter a series of chainage and offset pairs using a simple dialog box.  The convention for the offset is that negative is to the left of the reference line, as shown in the example, and positive below.  For this option, the Plan Chainage check box becomes visible but will only be enabled if the Linear Interpolation height method is set.  If checked, the distance you enter will be assumed to be the plan distance to the new point.  If it is not checked, the distance will be assumed to be the slope distance to the new point.  The Relative height method will calculate heights based on the first point and the Linear Interpolation height method will interpolate along the indicate reference line.

The Tied Distances method allows you to calculate the position of points that are of a known distance from two reference points.  Firstly, you will be asked to indicate the two reference points.  You will then be asked to enter a series of distance pairs using a simple dialog box.  Checks are made to ensure that the entered distances are valid.  They are valid if the sum of the two is more than the distance between the reference points and the difference between the two is less the distance between the reference points.  The convention on whether the calculated point is to the left or right of the reference line is based upon the sign of the distance from the first point.  If this distance is negative, the point will be to the left, as shown in the example.  If it is positive, it will be to the right.  The Relative height method will calculate heights based on the first point and the Linear Interpolation height method will project the calculated point onto the reference line and linearly interpolate using the projected position.

The Perpendicular Offsets method allows you to insert points that are perpendicular to a reference line that changes after each new point is created.  Firstly, you will be asked to indicate the two points which form the first reference line.  You will then be asked to enter a series of perpendicular offsets using a simple dialog box.  In this way, you can generate a building outline from one side and the lengths of other sides which have been measured using a tape.

In the example shown above, the first calculated point, 3, is calculated by using the indicated reference line points, 1 and 2.  The second calculated point, 4, will then be calculated using the first reference point and the first calculated point, 2 and 3.  The third calculated point, 5, will be calculated using the first and second calculated points, 3 and 4.  The convention for the offset is that a negative offset will create the point to the left of the current reference line.  Note that for the first calculated point, it is the first point on the reference line that is used.  For the second and subsequent points, it is the second point on the reference line that is used.

The Bearing Intersection method allows you to calculate a point that is of known whole circle bearing from two reference points.  Firstly, you will be asked to indicate the two reference points.  You will then be asked to enter a series of whole circle bearing pairs using a simple dialog.  The bearings should be entered in the angle units set in the current defaults.  A check is made to ensure that the lines created by the reference points and the entered bearings intersect.  The example shown below shows an invalid pair of bearings, where they diverge, and a valid pair of bearings, where they converge.  For this method, the Linear Interpolation height calculation is not available.

The Parallel Bearing & Dist option allows you to calculate a point that is a known distance from a reference point at a bearing that is defined by two further points.  Firstly, you will be asked to indicate the reference point follows by the two points that define the bearing to use.  You will then be asked to enter a series of distances from the reference point at which to create the new points using a simple dialog. In the example shown below, point 1 is the indicated reference point, points 2 and 3 define the required bearing and points 4 and 5 are the new points that have been created at known distance from point 1.  For this method, the Relative height method will use the reference point its calculations whilst the Linear Interpolation height calculation is not available.

The Sphere Centre option allows you to calculate the point at the centre of a sphere defined by four other points.  You will be asked to indicate the four points in turn.  The points must be 3D and, since the height of the new point is calculated in the algorithm, all height calculation methods are disabled.  This insert method is used for registering scanned data.

The Four Point Intersect method allows you to calculate the point at the intersection of two reference lines.  Firstly, you will be asked to indicate the four points that make up the two lines.  The first and second points will be assumed to be the first line whilst the third and fourth points will be assumed to be the second.  For this method, the Relative and Linear Interpolation height calculations are not available.

The Height of New Points

The Height Calculation group defines the method by which the height of any new points is calculated.  These are as follows.

Typed - For each new point, you will be asked to enter a value for the height.  Where possible, the value of the height will be asked for in a dialog box that is asking for other required data.  If no other data is required, a simple dialog box asking for the height will be displayed.

Relative - Each new point height will require a relative height offset from the first reference point that is indicated.  Where possible, the value of the height offset will be asked for in a dialog box that is asking for other required data.  If no other data is required, a simple dialog box asking for the height offset will be displayed.

Null - The new point will not be given a height and will be assumed to be 2D.

Constant - The Constant Height field in the Parameters group will be enabled for this option.  Each new point will be assigned the value in this field.

Linear Interpolation - The height will be calculated by linearly interpolating between two of the reference points.

Near Neighbour - As each point is created, you will be expected to indicate a series of points which are neighbours to the new point.  A weighted distance algorithm is then used to calculate the required height.  The further an indicated point is away from the new location, the less effect it has on the height.

Model Interpolation - The Reference DTM combo in the Parameters group will be enabled for this option.  The co-ordinates of the new point will be used to interpolate a height from the selected DTM.

Above DTM - The Reference DTM combo in the Parameters group will be enabled for this option. A  height will be interpolated using the co-ordinates of the new point and you will then be asked to enter a height offset which is added to this.  Where possible, the value of the height offset will be asked for in a dialog box that is asking for other required data.  If no other data is required, a simple dialog box asking for the height offset will be displayed.

Constant Above DTM - The Reference DTM combo and the Constant Height field will both be enabled for this option.  The co-ordinates of the new point will be used to interpolate a height form the selected DTM and the value in the Constant Height field will be added to this.

Model Trend - The Reference DTM combo will be enabled for this option and will list all the DTMs that currently have DTM trends created within them.  This DTM trend is then used to calculate the height.

Indicated Text - As each point is created, you will be asked to indicate a piece of text which is in the CAD backcloth which contains the point height.  The text that is indicated can have prefixes and suffixes to it and these will be removed.  For example, if you indicate a piece of text with the string CL=86.456m, the value 86.456 will be assigned to the point.  This method is only available with the Sketched insertion method.