Settlement Accesssubility: A case study in the south east part of chiangmai city, Thailand
This ILWIS software was used to create a graphic and attributes data base first the lineation from aerial photographs were transport to a base the settlement delineations are stored in rasher format the attribute data base is created based on the interpretation of aerial photographs and secondary data transport.
After finishing interpretation a field survey took place in the study area these are two aims in the field survey check and improve data from interpretation of aerial photographs and collect additional data that can not gathers from aerial photographs for instance public transport line.
The technique used for field checks in the study area is a combined random sampling this means checking of all settlements as mapping unit and in each settlements of the parameters are checked randomly
The data base of settlement accessibility after the field survey are indicated in future and table data about pattern density of houses in the mapping unit are also incident density of houses in the mapping unit are also included this data wilt be used to fid correlations between accessibility and type of settlement.
Accuracy Test
Comparison of the result of the photo interpretation and the actual situation the field interpretation about the accuracy of interpretation in general after checking in the accuracy of interpretation appeared to be accurate for instance the accuracy for the parameter width the street are about 80% for both major and local street and for their quality is also about 80% for major street and less than 70% for local street.
Width of street was measured directly from the photographs by using a magnifying glass with millimeter scale. Most in accuracy in measurement on photographs occurred because the edges of the street were not easily describable especially when not located on an open area other in accuracies in the measurement are caused by radial displacement of aerial photographs are occurred by high objects because of the displacement.
Quality of street is identified based on three main keys lone pattern and texture for instance surfaces street are mostly regular pattern smooth texture and dark tone asphalt or light tone for concrete material but it is not easy to different between payment street with surfacing and without different between payment street with surfacing and incorrect interpretations of the quality of street in a shadow area most street is caused by shadow of high objects on the street others are caused by some new streets they have same the tone as payment street.
Value of the parameters
For analysis data settlement accessibility from photo interpretation and field survey are normalized with values. The value range from 1to3. To desire the value of the parameters two approaches were used to decades on street consist width and quality of street in both major and local are determined with general street approach and the scale condition and payment with surface is better than others values are according to the class conditions the higher value the better condition class and values of the parameters are presented in table 1 to 3
Table 1: Class and value of parameter width of Major Street
| Class |
Width |
Value |
Remark |
| 1 |
> 7.9 |
3 |
two ways street for most of car |
| 11 |
5.0-6.9 |
2 |
two ways street for small car |
| 111 |
< 4.9 |
1 |
one way most car |
Table-2 Class and value of Parameter quality of Major Street
| Class |
Quality |
Value |
Remark |
| 1 |
Payment with surfacing |
3 |
Most comfortable to pass |
| 11 |
Payment without surfacing |
2 |
Comfortable to apses |
| 111 |
Un Payment |
1 |
less comfortable to pass |
Table-3 Class and Value of Parameter width of Local Street.
| Class |
Width |
Value |
Remark |
| 1 |
> 5.0 |
3 |
two ways street for most of car |
| 11 |
3.0-4.9 |
2 |
most of car can pass |
| 111 |
2.9 |
1 |
most of car not pass |
To decide the value of the parameters, two approaches were used. Conditions on street parameters, consist, width and quality of street for both major and local are determined with qeneral opinion approach, and the scale of the value is 1-3. In general the wider street reflect the better condition, and pavement with surfaceing is better than others. Value, the better condition. Class and value of the parameters are presented in table1 4
Table 4. Class and value of Parameter quality of Local street
| Class |
Quality |
Value |
Remark |
| 1 |
Payment with surfacing |
3 |
Most comfortable to pass |
| 11 |
Paymentwithout surfacing |
2 |
Comfortable to pass |
| 111 |
Un Payment |
1 |
less comfortable to pass |
