TheoLt: Powerful Flexible Features.

One of the great advantages of TheoLt compared to other survey software is it’s complete flexibility.  For example, lets take a look at the “Features Library”.

The basic premise of TheoLt is that it transfers the measurement information or point from a survey instrument (or Distance Meter) to CAD to be used by any command  (for example, draw lines, insert blocks etc). What the TheoLt Features Library enables is for a series of measurements to be combined to insert a series of lines, arcs or attributed blocks (much like standard survey “feature coding”).

The feature definitions are accessed through the the settings dialog in the main TheoLt window. Definitions are grouped into folders.

Looking at it’s simplest use, inserting a single attributed block as a detail point. The first stage is to name the feature , define it’s icon and the number of measurements that should be taken to insert the feature. In this case, a single 3D measurement.

The next stage is to define any user attributes that may be required and whether confirmation is required (asking the user to confirm the values). Finally select the block to be inserted.

Once defined, opening the features panel will show the newly created item and a single click on the apropraite icon in the feature  palette will prompt for the measurement and the block will be inserted.

Next we can look at a more complex but typical use; kerbs tops and bottom in topographic survey. The aim here is to pick points on the top and the bottom of the kerbs, connecting the points, inserting blocks and annotating levels. This is very typical of topographic survey. Our definition will be point on top of kerb, point on bottom of kerb before moving on to the next part of the kerb.

Defining the feature, we name it and use 2 3D measurements with correct prompts. As we wish to join the points with lines, we will select “repeat insert” and join points on Layer (each point type having it’s own layer). This will allow the lines to be continued for as many measurements as required before exiting the command.  The attributes will be the Z-level of the first point only and two blocks will be inserted, each on it’s own layer.

Now when selecting the feature from the palate, the measurements are prompted, blocks are inserted and then the first prompt starts again. After the next round of observations, lines are drawn between the respective points on their designated layers. Options allow the lines to be curved, straight  and the alignment of the annotation to be altered or disabled.

The final example is a single complex item; a tree. To measure one fully quite a few measurements are required; the centre of the main trunk, the girth of the trunk, horizontal extent of the canopy and finally the vertical extent (height). These can be defined in the first window with prompts and measurement types. I would assume that for the first measurement the operator would take the angle to the centre of the trunk before taking the distance to the centre. This would leave the instrument pointing to the extent of the girth which we can collect as an angle only measurement. We can also choose to write the details out to a file which can contain any of the collected data fields for processing.

Next we will create the attributes where we will also collect the tree type which will be stored in a list to speed up the user input.

Finally we insert a block to represent the trunk – scaled to match the girth. A second block will be inserted, scaled to math the canopy.  An attributed block is inserted to hold the details of the tree (in addition to the file written above).

Obviously, this is not an in-depth analysis of what is possible from the features palate but I hope it gives some indication of the power within TheoLt.

TheoLt PRO: Traversing

These days big traverses are becoming a rarity. The GPS active net is doing a better job for many survey projects. Traversing is still the best way for getting good control for small sites, setting out, architectural photogrammetry and building survey. I remember the happy time at field school in Wales with booking sheet and pencil, baking in the summer sun, each station in turn becoming a kind of holiday home as we carefully logged back-sight and foresight obs. We got to live outdoors and enjoy it. So, given that this is the backbone of my work, why do I hate it so much?

It is the inevitable disappointment when, at computation, I discover the blunders! All the wonderful effort of getting stations set out, carrying forward heights, multiple obs is lost when the numbers don’t come out! Each time I set out to traverse I have the optimism of a child on a trip to the seaside only to face the bitter disappointment of having to repeat the work to get it right. This is something I have grown used to: traversing is a game of errors and I have, over the years, found out how to get the results I want. In truth I have never been happy with simply surveying for numbers, for me I want to see a drawing, detail, I want that map to grow, to make my mental map real; a schedule of co-ordinates to me is no thing of beauty. So what to do about it?

I can’t do my job without control; I’ll never forget the wise words of Peter Waldhausl when I asked him the teacher’s question: ‘what is the single most important thing to teach in survey?’  his answer, without hesitation, was very clear: ‘NO ACTION WITHOUT CONTROL!’

It’s thrilling to drive in the first peg on un-surveyed territory, this is without doubt part of the elemental appeal of surveying (it’s certainly is NOT the money…few of us are well paid and even fewer of us manage to keep our jobs!) we are part of making the unknown known in a very real way. Anxieties about control can be helped by getting the right tools and first and foremost in these tools is software! I use real-time software that tells me where I’m going wrong when I make the mistakes. Now I know this is not proof against blunder but it definitely helps! Keeping track of where the errors are is one thing but I’m amazed at how much gets in the way of your best rehearsed procedures when you are traversing: for crying out loud there are only 4 things to do:

1. Log the instrument and target heights of collimation (HoC).

2. Achieve and verify orientation.

3. Observe and book shots to back-sight & fore-sight.

4. Set out new station as required.

So what goes wrong?

Plenty! You forget which station you are at and use the wrong station ID, you set out a station then find the sight-line blocked, somebody ( it’s never you!) kicks a tripod and you have to re-set the HoC and retake the station orientation, you select the wrong HoC for the orientation shots, you forget to take the last angle in the loop because you think you already have the shot done as you have ‘been here before’ not to mention the lost marks, last minute datum changes, miss-matched tribrachs, ‘helpful’ people moving setups before they are measured, it starts raining etc.

The software definitely helps, I have a strong tendency to argue with it but I’m learning to trust it (yes I’m pretty stubborn like that I’m afraid).  The Netadjust tool in TheoLt Pro is what keeps my traverses on the straight and narrow.

It has some really good ‘idiot proof’ features which this idiot has learnt to adopt as procedural reinforcement:

Real-time feedback of station selection at occupation and orientation. I get a ‘heads up’ message on completing an orientation that advises me of the staion IDs, the HoCs and the precision of the orientation.

Automatic prompting of HoCs. Every time I take shot to a target I get a prompt, I can turn this off, but this is my most common foul up, its very difficult to ‘unpick’ HoC errors even though it is usually very easy to see where they occur.

Traffic light coloured observation results. This really is the best bit for me, TheoLt will let you know how good your shots are as you take them, you can drop the ‘bad’ obs from the computation, re-shoot or go right back and re-do the orientation again.

Automatic target ID. When you shoot a target with a known position you are prompted with its ID, a simple hint saving a mountain of time searching through tables to find a station ID.

Live diagram. I can preview my loop in AutoCAD/BricsCAD at any time; if it don’t look right it ain’t right. The diagram tells the story.

Non destructive back-up of raw data.  You can run the calc and see what happens at any point in the loop and still have the original observation data logged for QA.

Least squares distribution of error. TheoLt through its partnership with kubit uses a powerful network adjustment algorithm. By moving away from Bowditch (sob!) towards a distributed error network the traverse can be extended to include resections.

TheoLt orientation procedure builds the network data table which shows how good the shots are, how many shots there are in the set and allows you to include or exclude a shot from the computation. I can get reports out on the condition of the network when I run the calc to test the impact of the include/exclude options I use:

Let’s take a look at the report:

TheoLt NetAdjust does traversing nicely but there are drawbacks, its not something I would expect the whole survey world to use. It’s dependent on a PC so its not going to be what I would use on a windswept fellside in driving rain. For me it’s a godsend simply because I can get good control without fuss and move on to what I want to do…draw!

Control networks are essential for a complex building plan. The exterior can often be controlled by a fairly traditional loop with some fun & games to accept GPS points. Once tied to the exterior loop the interior can usually be fixed by resection throughout.

There is always something that gets in the way!

A control network needs to provide points with a higher order of precision than simple polar observations. Easy to say, a fiddle to do, but a whole lot simpler with TheoLt!

More on the TheoLt story here:

TheoLt: The CAD in CADW Surveys!

This week I spent two wonderful days as a guest of CADW working at Chepstow Castle.

CADW site listing and…History of the Castle

The castle is a gem, and it was a privilege to be shown some of its secrets by the conservation experts I was working with. We had awful weather but we didn’t mind, as working together, we were able to get a good plan of the 2nd floor of Martens tower and, for me at any rate,  this is the finest kind of work there is!

The Architects Dept. of the national heritage body for Wales need surveys for site conservation and development. Following a demonstration at the Digital Past event in Cardiff earlier in the year the Architectural Technicians Team bought TheoLt Pro to work with their Leica 1200 series instrument.

I agreed to supply 2 days of  ‘on demand’ training for Paul Hayes, Michael Hopkins and Tony Kinson who handle a variety of challenging projects which need critical survey information in real-time.

Survey is a key tool in site development of any kind, and heritage sites have very specific survey needs. The CADW team get most of their survey done by contract survey companies working under a framework agreement, but there is a constant need to get small tricky areas surveyed quickly to kick off a design scheme for new visitor accommodation such as ticket offices, access pathways and the like.  Surveys need to be quick, in CAD, and annotated with levels in plan section and elevation.

The training session began with a quick assessment of training need and moved straight into practical procedures: getting a quick survey started using default orientation is a very useful way of getting the most out of limited site time, and the TheoLt ‘Default orientation’ option proved the point- once the kit is set up you can begin collecting precise 3D wire frame in minutes!

Its worth remembering TheoLt was designed for just this kind of scenario; a CAD plot of a single wall profile can make all the difference in project design and the software puts the absolute minimum between the surveyor and the CAD drawing. The CADW team are focused on solving project information needs and were impressed with the direct to DWG approach.

Working as training and support for Latimer CAD I find building a good relationship with TheoLt users rewarding and fun: its great to know CADW are able to get the most out of their 1200 now they can work with TheoLt!

We quickly worked through our training agenda:

  • Quick start
  • Preparing plans
  • the 3 methods of orientation
  • using UCS for 3d views
  • handling linetypes and line typescale
  • checking precision
  • level annotation using attributed blocks
  • toolbar customisation
  • working with AutoCAD alternatives- BricsCAD
  • TPS 1200 interface.  the pdf on this is here

Getting to know the ‘most wanted’ AutoCAD commands in surveying turned out to take up almost as much of our time as getting to know the TheoLt interface, this was no surprise to me as I know when TheoLt is used well it’s virtually invisible, making the job an AutoCAD one rather than a surveying one!

CADW need sections, levels and plans of the ‘hard to reach’ parts of their monuments and sites and this is just where the flexibility of TheoLt is an asset to the CADW team. At the very beginning of our session I was told the frequency of survey activity in the workgroup was very variable and they needed a method that is simple enough to pick up months after last use.  By the time we packed up at the close of the session I was cheered to hear user comment like ‘this is so much better that what we did before; you can see your mistakes as you make them!’

Driving home along the banks of the River Severn I was reminded of my first days doing CAD surveys and how often I would get stuck and have no help at all ( it was ‘PenMap’ in those days) and I look forward to the CADW teams first site survey with TheoLt because, of course, I’ll be there if needed to build the skills required; I have opened the door of opportunity for these surveyors and I am proud to have been invited to do so!