Ping this blog! Plane table into CAD software

Well the attached image shows a rather failed attempt to pioneer a process honoured by the ancients, yet never before brought kicking and screaming into the modern era, and shows huge potential, in my humble opinion. Plane tabling is what mapped thw vast expanse of America before the theodolite came along, it is simple and yet has been abandoned in favour of the more complex specialist approach. I believe bringing back the plane table, together with a modern approach using an Android Phone’s GPS function, may democratize mapping and surveying again.

The rather messy graphic JPEG shows my attempt to enter the data I obtained in my garden last summer – I did the survey 11 June 2013 – last summer! so forgive me for not entering the data correctly. The other issue I had was which sofzware to use and I chose Microstation as I had an old copy lying on my PC – I am an old cartography bloke you see.

So what did we learn from these rather scrappy initial efforts? That a single sheet per station surveyed is the way to go, to collect clean angles and avoid ambiguity. some insight was also gained into how to store the data one day perhaps inside the Android phone, in some kind of database, should we get that far.

So here is the rather lousy incomplete image of the house and garden surveyed. Bear in mind that I am l relearning Microstation having not used it in almost a decade.

 

Garden

 

 

 

 

 

 

azimuth

Okay so I with my limited experience of event driven programming, managed to enter some code from a tutorial on MIT app Inventor which polls the orientation sensor of my mobile and outputs the points of the compass.

To recap, here are the three steps I am attempting to accomplish:

1. Obtain a weighted average GPS reading from a stationary GPS on my plane table.

2. Calculate bearing and distance into Cartesian points

3. Plot the derived points into a CAD system.

 

Keep it Cartesian!

Okay so yesterday 20June I was out inthe garden and managed to collect a fullset of coords using my plane table. Here is the data. Needs heavy organising!

All angles run in clockwise direction from both stations.

Station 1:

N47 deg 52.346 E11deg 41.684 (4.5m error)

Ray# distance (m) angle               description

1            10.25              115                 corner of lindlfeldweg/bergfriedstr

2           23.45               245      corner adjacent to markus house

3          17.6                  252      bearng/dist to station 2

4           6.7                   286         south wall (right)

5           8.9                    307        left of front door

6           7.1                   333        right of front door

7          18.9                  348         ne corner of house

8           15.1                 353            ne corner /L shaped wall)

Station 2:

N 47 deg 52.340 E11 deg 41.684 (6m error)

1           17.1                     7                  nw corner of house

2           6.6                       38                sw corner (tomatoes)

3           6.2                      145               sw corner border with marcus

4          19.8                   335             nw corner of garden

 

So, from this data we ought to be able to develop some kind of plotting “language” algorithm. Stations ought to be separately specified in the new “language”.

The next mini project ought to be finding a way to plot this data.

New plane table?

After the efforts of the last time, I have found an old piece of laminate flooring 120cm long by 19cm wide which may be pressed into a new plane table. Given that the standard tables seem to be about 65 x 47 x 1.5cm perhaps two sheets may make a decent space to work with.

Importing vertices into Sketchup

Okay so far we have three usable coordinates:

2 4.73 House corner
275 2.92 House corner
314 5.29 House corner

All 3 are in the format <length> <angle> and need really to be in the format <length> <length> as construction lines for my house outline.

This is certainly one of those sine calculations (opposite/hypotenuse) to gain the opposite end of the construction line needed to draw the house outline.

I downloaded Trimble Sketchup to see if we can draw a house outline using this method.

A lighter board to use.

Design idea for plane table Mark III coming up. I am going to dig out some old laminate flooring waste boards I have been hanging on to for ages. The present table is too heavy! Commercially sold tables have dimensions of A2 paper size or 650 x 470 x 15mm so this will be the size we try.

Challenge is to devise an attachment system onto the tripod.