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.
   
   
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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.

Sources of Information

Accounts on the history and architecture of Assam are scarce. However and important source of information about the Ahom dynasty are the Buranjis; accounts originally in Assamese, written during the Ahom rule (13^th-18^th Century approximately), under the commission of Ahom kings as a narrative to their rule. Hence, the historic information in these accounts is limited and is covered in myths and legends.

The ASI used to maintain a log of work and condition as site inspection note books, drawings, photographs and estimates of works undertaken on protected structures, on a regular basis. Though this practice may not be regularly maintained, the older logs form an important source of information on the history of conservation of the buildings.

We rely heavily on the first-hand information i.e. the building and the site as the starting reference. Later, we shall be contacting relevant resource persons and other archival material to support our findings. A series of non-intrusive and non-destructive investigations i.e. material studies, condition of foundation and monitoring of cracks and building movements have been proposed and are yet to be undertaken. Specific tests and processes will be mentioned in the relevant sections.