updated: 26-Nov-2009

 Copan for Windows

Map Traverses

Contents

Azimuth (or bearing) and distance traverse data, common on many cadastral maps and plans/plats, can be used to calculate new points. Use this module to compute and adjust for misclosure any number of such traverses, including ones with curves, and save the new points whether or not the traverse is open, closed or adjusted, and calculate lot/parcel areas.

Note that if you are just checking bearing and distance traverse data, and not using a coordfile, you should use the § Map Check module.

Also, this module cannot be used for field data, involving horizontal or vertical circle readings. For such needs, use the § Field Data Processing module or its Field Bearings variation. While there are certain similarities between the Map Traverse and the Field Data modules, there are various operational differences (other than the type of map/survey data involved). If you are familiar with one and new to the other, please study the appropriate manual and dialog carefully.

1. To Adjust Bearing-Distance Traverses

1. Calculate | Adjust Brng-Dist Traverse (Map Trav)...
2. Optionally Load... a traverse Data file (see Map Traverse Files below).
3. Optionally enter corrections: an Azimuth Correction, to be added to every bearing; a Units Factor, for converting distance units to coordinate units; a Projection SF, for the map projection scale factor correction.
4. Enter or edit the bearing-distance traverse data in the big edit box. See below for a description of map traverse data for adjustment.
5. Editing traverse data in the big edit box:
   To move the text cursor within the box, use the Arrow, Tab, or Enter keys, or the mouse pointer. Do not use the Space key to separate fields. To delete a chunk of text, select it with the mouse then click Cut (or type Ctrl-X) but be careful not to delete the embedded tabs within a line. To manually insert a tab, Copy and Paste an existing one. The Ctrl-Insert and Ctrl-Delete key combinations act like the Ins and Del buttons, that is, they insert and delete a line of data. To add a Point number automatically to the next blank line, press Enter when in the Distance column of the previous line.
6. Optionally List the map traverse data.
7. Optionally Export.. in ESRI format or Reverse the direction of the map traverse data.
8. Optionally check the Auto insert proper AC box to have an azimuth correction automatically inserted at the start of the traverse such that a recalculation of the traverse would have no overall azimuth error.
9. Save the Data for reuse.
10. Calculate (or OK) the traverses, adjusting each one as desired (see § Traverse Processing).
11. To graphically view the traverses: Close or hide the Info Display window if it is open, and minimize or move aside — but do not close — the Map Traverse window. You may turn off the annotations prior to Calculation if desired.
12. Optionally choose whether to Renumber new points or replace existing points (see § Point Renumbering or Replacement) and Save the Points that have been computed.
13. Optionally List the Points that have been computed.

click for larger view

2. Map Traverse Data for Adjustment

• Begin each traverse by a starter line, which must contain the first point number, under Point, and may contain a traverse label, under T-Label, identifying the traverse.
• If you have multiple traverses, when you Calculate you may begin from a specific traverse rather than from the top by entering the start point number or traverse label.
• The first point must already exist in the current coordfile or be in a prior traverse.
• A traverse must have a sequence of leg lines. Each leg
  • must contain these three items: to Point number, Bearing (or direction) and Distance,
  • and may contain a P-Note, P-Code, and a Curve code (see § Traversing Curves on how to define curves along a map traverse).
• For a Bearing or Distance, a bearing or distance expression may be used (see § Bearing Expressions and § Distance and Offset Expressions), or, if it is the same as the previous one, a double-quote character (") may be used for ditto.
• If points are saved, P-Notes and P-Codes are added to the point.
  NB: If a point appears in more than one leg and is saved, its later Note and Code may replace its earlier ones.
• A closed traverse, where the last point is known, may be adjusted or not. An open traverse (where the last point is unknown) is allowed.
• Treat side shots as separate, single-leg, open traverses.
• At any point along a traverse you may need to change the scale or distance factors or the azimuth correction. To do this, enter a separate line with
  • SF=value,
  • UF=value, or
  • AC=value
  under Correction. From that point on the new value is used instead of the original head value. Optionally, a differential azimuth correction
  • da=value
  may be used, where the value is added to the current value for subsequent azimuth corrections. Or, a relative azimuth correction
  • ac=value
  may be used, where the value is added to the original head value for subsequent azimuth corrections. Note that these commands are case-sensitive.
• Blank lines may be used for readability but have no affect on traverse demarcation or calculation.

3. Map Traverse Files

• The first line must contain only this text:
    Map Traverses
• The next three lines can contain anything as they are not currently used.
• The next three lines must contain the head correction values — Scale factor, Distance factor, and Azimuth correction — one each per line.
• Each subsequent line must be either a comment line or a tab-delimited data line with these six fields:
      Point, Bearing, Distance, Label/Note/Correction, Code, and Curve
  While some or all of those fields may be empty there must be five tabs per line. Which fields can be left blank depends on the purpose of the particular data line (see § Traverse Data for Adjustment above).
• A valid comment line begins with zero or more spaces or tabs, then has two commas (,,), periods (..), slashes (//), semi-colons (;;), or backslashes (\\), which are followed by any character string. Comments are not processed or stored as point notes (but are saved within the traverse file). Use them to temporarily remove an observation or to annotate a traverse.

4. MT File Examples

Example 1:   Two simple traverses.

Map Traverses
1st dummy line
2nd dummy line
3rd dummy line
0.9997670000
1.0000000000
0.0000000000
9009                           primary
1463     235.2547     061.29
1462     255.1305     215.44
1461     232.3944     028.45
1460     182.1748     161.24
1464     272.0355      125.98
9008     217.3139     087.16
1461                           secondary
1465     092.2112     160.40
1466     182.0352     160.93
1467     "            040.72
1468     "            007.60
1469     183.4005     059.19
1470     260.5657     160.73
1471     000.0812     061.41
1460     002.1748     077.60

Example 2:   A traverse with curves.

Map Traverses
Copan
V07152.pts
C:\Documents and Settings\martinf\My Documents\Whistler\13031.mt
1.0000000000
0.3048000000
0.0000000000
5746
                               AC=-0.0436
5819     089.1140     166.64
5820     s11.5550w     34.06
5821     "            108.57               bc
5827     s78.0410e   3105.89               cc
5823     n79.1910w     "                   poc
5822     s79.1910e   2342.01               cc
5824     n89.4134w     "                   poc
5822     s89.4134e     "                   cc
5825     s89.1943w     "                   poc
5822     n89.1943e     "                   cc
5826     s86.3512w     "                   ec
5787     w           103.24
5788     s08.02w      46.4

5. Curve Adjustments

If a traverse that contains curves is adjusted, its curves are affected as follows:

• For non-tangential curves, the curve chords are treated as traverse legs for the adjustment, and then the curve centres are recomputed based on the original curve radii and new curve begin-end points.
• For tangential-curves, the external tangents are treated as traverse legs for the adjustment. The curve begin-end points are recomputed based on the new curve intersection points and external tangents, and then the curve centres are recomputed as above.

6. Export

Use the Export... button to export the current map traverses (starting from where you specify), in ESRI Traverse File format. You specify the location and file name (the default being the current folder and current map traverse file, without the .mt) and Copan will save to file-name\file-name.txt (that's the funny way ArcGIS expects it). It uses the saved coordinates for the start and end of each traverse, and the interpreted (after corrections have been applied) but unadjusted map traverse data.

7. Reverse

occasionally, you'd like to use an already entered traverse but in the reverse direction. Use the Reverse button to reverse the current map traverses (from last to first), each one in reverse point order. It uses the interpreted (after corrections have been applied) traverse data, so if you want the raw data reversed, you must first temporarily remove the corrections.

8. Notes

• If a traverse is a true loop (i.e., it closes on itself) Copan provides the enclosed area in squared distance units (e.g., m²).
• Copan does not yet calculate areas that are only enclosed by separate different traverses.
• If Copan complains about the data when calculating, and you cannot see what is wrong, visually inspect the data by selecting it all with the mouse. Often, you can see the inconsistency via the selection block outline.
• List All... is equivalent to the sequence List data, Calculate, and List Points.
• If you List traverse data to the Info Display file,
  • multiple blank lines are ignored, and
  • azimuth (or bearing) and distance expressions or dittos are shown in their interpreted, but not corrected form.

9. Bugs

• Traverse graphics annotations are not currently working properly.

updated: 26-Nov-2009