Step 01 : Identifying approach, process and information to be collected

Our Project brief requires us to prepare manually measured drawings, the basis on which conservation work of the structure and fabric can be directed.

A - Preparation to Work - Reconnaissance survey was conducted of the building, whose base measured 25 mt   by 18mt, having 4 floors (12 spaces in the ground floor, 8 in the first floor, 5 in the second floor, 2 in the third floor and terrace). Based on the drawing provided by the ASI, the spaces were numbered as S1 to S-N, in an anti clock-wise manner (Refer to Photographs- Naming of Spaces and Phasing for Measurements) and a reference diagram was made prior to commencement of  work.  

Naming of Spaces and Phasing for Measurements

B - Identifying Tools - Given that the work was commissioned to only 2 people, a process that provided accurate information yet is time efficient has to be selected. Also, in the absence of standards tools - such as a laser-cross-hair, inclinometers, disto-meter, total station, auto-leveler, digital spirit-level, the method to be resorted had to be manual, with basic tools - spirit level, string, chalk and measuring tape. Therefore, the schedule of work and time-frame had to be revised.  

C - Identifying bearing points and measurements - It was decided by the consultants that the built profile (floor plans) would be drawn by triangulating from an established reference plane. It must be mentioned that the reference planes are normally established outside the structure to be measured. However, in this case, fixed bearing points available are more than 8 meters from the built profile. Over this length, measurements taken are erroneous due to sagging of the tape. Moreover, the site being overtly visited, it is impossible (also requiring permission) to erect a temporary bearing point which will last 6 months (the length of project time). As a result, it was decided that an internal-grid would be established, from which measurements for the internal profile would be acquired and later, from the elevations, the external profile would be drawn. 

D - Phases of work - First, the profile of the interior spaces would be drawn, thereon, smaller details, that measure less than 1 meter i.e. mouldings, interior of niches, details and the profile of the floor, would follow. (Refer to Photographs - Phases of Work - Measured drawing of Floor Plan along established Datum Line)

Phases of Work - Measured drawing of Floor Plan along established Datum Line

Following the profile of the floor, would be the external elevations. For this a vertical reference grid at 2 meters interval would be established and measurements will be taken by a combination of methods - i.e. by triangulating and from rectified photographs (Refer to Photograph- Vertical reference grid along the North Facade).  

Vertical reference grid along the North Facade

E - Tests and Assessments - Based on the reconnaissance survey, a list of tests were also recommended as necessary- 

• Tell-tales along cracks, separation joints which are possibly active
• Excavation along at 4 points to assess condition of foundation (before rain)
• Tests to identify composition and condition of plaster, mortar, bricks, flooring material (at different level and points)
• Noting of changes in moisture levels, rising dampness etc

Step 02 : Establishing a Datum Line

The first step towards architectural measured drawings was to establish a datum line i.e. a section plane that becomes a horizontal reference plane at which the plan is drawn. Usually this horizontal plane is established at a level of 3 feet or 900mm from the floor level, explaining all recesses, projections and other details, that comprehensively reflect the building and its defects (like settlement, movement of members, inclinations etc). However, in the case of Karen Ghar, datum line was not established with respect to the the floor level, as the latter differed at different parts of the building. Also, a section at 3 feet would only provide partial information of the built profile, hence, the level was selected at an average of 920mm-1000mm from the floor that provided the profile with all openings, niches, recesses, mouldings etc.

Initially the marking was done using a string, white chalk and plumb bob, of which the latter was replaced by a spirit level (manual). The string was held tort at two ends – from a marked point on the building to a corner or point in the building to be marked. The level was checked using a spirit-level for horizontality and marked using the chalk. (Refer to Photograph - Marking the Datum Line along built profile)

Marking the datum line 

Step 03: Field Sketches

  For field sketches, the following are being used:

a.      Graph paper of A2 size (594 x 420 mm) with grids in centimetre

b.      A3 transparencies

c.      Drawing board of size A2

d.      Pencils with 0.5 mm leads

e.      Scale (30 cm)

f.       Cello-tape to secure graph paper         

1. An indicative plan with spaces in the ground floor labelled S1, S2, S3….S15 is used for reference.
2. The team has started with noting interior measurements. We are following an anti-clockwise order for measuring interior spaces.
3. A proportionate sketch of the room plan, along the marked datum line is first drawn on the graph paper. On each of these sheets, details such as Structure code, Content, Date, erroneous points, corrections are being recorded.
4. In our initial stages of noting measurements, the sketch plan included even the details (niches, moldings, archways etc) and dimension lines were drawn between every point in the room. But this method resulted in confusion, making it difficult to comprehend the sketch and causing errors while draughting. 
5. As the team is severely short of working hands and time, it was not possible to draught manually on site. The noted points had to draughted off-site using Auto-CAD. We had to hence, adopt an easier yet effective way of noting measurements. It was later decided that we, first, label each point on the sketch plan alpha-numerically. The measurements between points are then noted beside the sketch itself. Although it is understood that this is not the technically correct method of recording, we have realised that this is the most effective method, under the given circumstances. Please refer to the following photograph for a sample work sheet.
6.  On completion of the profile of the ground floor (exterior and interior), an A3 print out of each of the rooms will be taken to work on the details.
7. A computerized log of all the field sketches is being maintained and will be submitted, for any future references.
   
   
8. 
   

Step 4 : Noting measurements

Instruments used

·         30  m measuring tape with graduations of 2mm each

·         15 m metal tape

·         30 cm scale

·         Set squares

·         Torch light

1. Before we began noting measurements, the working team had decided that measurements over 3000mm span will be avoided in order to minimise errors due to sagging of the measuring tape.

2.  Care was taken that the tape was always held vertical (i.e. perpendicular to the floor line) in order to minimise errors.

3. Wherever there was chipped, broken or loose masonry on the corners, care was taken to place the measuring tape on the marked point.

4. As the tape we use for measurements have graduations of 2mm, we are cautious while noting measurements.

5.  More than 2 measurements were taken for critical points to aid in cross-checking.

6. One of the limitations that we face on site even today, is the absolute lack of light in 3 interior rooms. Adding to the limitation is the large of the room (>5m x 5m). 

7. All dimensions are being noted in Millimetres.

Step 05 - Transferring Dimensions

Transferring dimensions collected must be a simultaneous process and completed on  site. Though it is better to draft manually, in this case it was directly drafted in AutoCAD2010. The first step was to make a proportionate sketch of the space to be measured, on a graph paper (millimeters). The sketch reflects only those points which help develop the profile of the space i.e. openings, prominent mouldings and corners. These points are then marked alpha-numerically and in order. Dimensions to be taken for drafting specific points are then identified. For critical points, especially those over 3.0 m in length, a second set of dimension are also taken as cross-checks.

Different methods were exercised to find an appropriate one to note dimensions. Initially, diagonals were drawn connecting two points between which dimensions are to be taken. The latter was noted in the form of 2.88.6 - i.e. 2 meters, 88 centimeters and 6 millimeters.  This system of noting, recommended by the HABS and HAERS systems proved to be cumbersome and confusing and hence restricted to room S1 alone. Thereon, dimensions were recorded as - 2886 mm and called out as 'Two Eight Eight Six' and noted on the graph paper as - 1- A : 2886m.

Recording dimensions at Site

The same dimensions as noted were transferred to AutoCad on site or at Office on return. Dimensions that proved erroneous were marked and verified either immediately or on the following day. 

On Autocad, the intersection of the arcs of dimensions are retained as a distinct layer - 'MD-Draft_Arc' and dimension lines as 'MD-Draft_Measurement Lines'. It has been decided that any point that provide the built profile would not be drafted in Autocad but be done manually, noting the undulations of the surface later. 

Transferring dimensions to AutoCad

Manual recording techniques: Part I

Documenting historic buildings, in India are restricted to protected structures and are performed only prior to execution of civil works. Architectural documentation as a part of Recording, Analyses of the structures is seldom undertaken. It is only post the World Heritage nomination initiation by the country that Architectural Documentation has been undertaken as a mandatory action. Since documentation is relatively a new practise, still met with scepticism, the necessity of use of new technology to aid documentation is met with a question. As a result, consultants resort to using manual methods of documentation.

“Manual recording techniques use tools such as plumb bobs, measuring tapes, and paper and pencil to record buildings or sites. Although often labor intensive, these techniques are readily available and allow the study of buildings or sites in great detail. Usually this method of recording provides sufficient information and accuracy with which to begin conservation.” Source: Glossary, Vol-II, Recording, Documentation and Information Management for the Conservation of Heritage Places. Los Angeles: The Getty Conservation Institute, 2007. 

The method of documentation is “triangulation”. 

Refer to: http://www.cr.nps.gov/hdp/standards/HABS/HABSrecording.htm

The tools that are currently being used for documentation are shown below. 

(To be read Clockwise)

A.  Chalk

B.  Measuring tape – 30 meters (canvas)

C.  String

D.  Spirit level

E.  Measuring tape – 15 meter (metal)

F.  Brick; to  weigh down string

G.  Set squares

H.  Cutter

  I.  Pencil