HW: Planimetric Mapping
Purpose: To learn how to survey and map planimetric (X, Y) features using a total station.
Equipment needed: Total station, Tripod, Prism and Telescoping Prism Pole, Cloth Tape Measure, Field Book
Field Notes: All measurements will be recorded in your field book.
Office Procedure:
Using the coordinates you computed previously in your traverse, compute inverses between your parcel corners. Also compute the inverse between these points and the control point on which you based your traverse. These azimuths will be used to orient your total station in the field.
Field Procedure:
Using your parcel corners as instrument stations, you will collect a series of radial observations (distance and azimuth) to determine the key planimetric features of your parcel. Radial measurements are observed when a number of points are surveyed from a single setup.
a) Set up the instrument on one of your parcel corners and backsight another parcel corner.
b) Set the azimuth on the total station to the azimuth you computed between your final adjusted traverse coordinates. Note the azimuth in your field book (as a BS)
c) To collect features such as a sidewalks, manholes, drain grates, planter beds, etc.:
- The rod person will find the edge of the feature and place the rod point on the edge of the object.
- When the rod is plumb, the instrument operator will measure the distance (horizontal) and azimuth to the feature.
- Note the point name (e.g. EOP1 or 189), distance and azimuth to the point as well as a brief description of the object. You can create your own abbreviations like EOP for Edge of Pavement provided these are spelled out somewhere in the field book.
- A features may require one or more points to adequately define it:
§ Manholes only require one point right in the center
§ A storm grate or square requires all four corners
§ Sidewalk boundaries need only be surveyed at bend or end-points
§ Curves and circular sidewalk segments require 3 points, one at each tangent point, and another close to the midpoint of the arc
§ When surveying object such as trees or light poles you will generally not be able to measure directly to the center of the object with a total station. You should place the prism besides the object for distance measurement (see diagram below), but move it to the center of the object to measure the azimuth.
§
§ If the diameter of the object is small, measure the diameter directly (to the nearest 0.01 ft. If it is large, wrap the tape around the trunk of the tree, measure its circumference, and then calculate its diameter to the nearest centimeter. Also estimate its crown (canopy) by pacing the diameter.
§ Your last measurement should be a check measurement back to the BS station. Note this in your field book and check that the azimuth matches your original setting.
§ You may have to move to different corners to collect all of the features in your parcel, but with a little planning, you can collect all of your data with the minimum number of setups.
Computations:
Use the Excel functions you have used previously to set up an Excel Sheet to compute the coordinates of your feature points. The columns of your sheet should contain the following:
Station Setup Point, Name and Coordinates; Observed Point Number/Name, Azimuth, Horizontal Distance; Description of Feature Point; Coordinates of Feature Point.
Mapping:
Following the techniques of Lecture: Mapping3: Planimetry on the course website, update your AutoCAD project map, adding points for each feature tied. Add lines connecting points if necessary for building sides, sidewalk/pavement edges, etc. Add text descriptions of the features. Show all tree trunks as a non-scaled symbol, but show the crown canopy to approximate scale. Delete features that were initially sketched in location.
Submit: In WebCT, upload TWO files:
1. Your Excel computation sheet showing the coordinate computations for each point. Scan or photo your field book and insert the *.jpg in the spreadsheet.
2. Your updated *.dwg AutoCAD map showing your mapped planimetric features.