Survey Control for I-205 Columbia River Bridge

The establishment of the principal control points required for the Columbia River Bridge construction using present day electronic distance measuring equipment is reviewed. Selection of the survey equipment was based on the distances at the bridge site to be measured and simplicity of operation. Familiarization and confidence were gained by traversing the river and verifying existing points set earlier by the location survey. The bridge site was studied and five locations were selected for permanent monuments. Shelters for protection of the instrument were constructed, distances measured and angles turned. Closure was made and coordinates determined with the aid of a computer terminal and the Highway Division COGO program. To date the bridge piers and some of the superstructure have been successfully positioned with a minimum effort utilizing the five control points. The electronic distance measuring equipment and computer terminal have proven to be a time and labor saving combination for establishing survey control of this type.