Wood River Bridge, AK

Background on the bridge

The community of Aleknagik, with a population of 197, is situated on both the north and south shores at the outlet of Aleknagik Lake as it flows into the Wood River [1]. Aleknagik's residents are primarily Alaska Native (91%) and belong to the Yup’ik-speaking Kiatagmiut people, whose traditional territory encompassed the Nushagak River drainage to the east, including the Wood River lakes and Aleknagik Lake [2,3]. In 1933, a school was established in Aleknagik, bringing together various communities to its current location. Subsequently, in 1959, a road was constructed to connect the south shore with the regional hub of Dillingham. The road underwent upgrades in the 1980s and was eventually paved in the mid-2000s.

The Wood River Bridge, completed in 2015, serves as a vital link between both sides of the Aleknagik community. Prior to its construction, access to the north shore, where the school, city offices, and tribal government offices are located, was primarily limited to summer boat travel, winter snow machine transportation, or small aircraft landings on the state-maintained runway [3]. The bridge has since facilitated frequent travel to Dillingham (population 2,226), a regional hub and one of the main harbors for the world's largest sockeye salmon fishery, the Bristol Bay fishery [4]. Dillingham boasts a paved runway capable of accommodating large jet aircraft, along with two grocery stores, a bulk food store, a bank, middle and high schools, the University of Alaska Fairbanks (UAF) Bristol Bay campus, a hospital, and various other amenities typical of a small city [5].

The construction of the Wood River Bridge had been a long-anticipated infrastructure project. Studies for the bridge's feasibility commenced in the early 2000s after receiving funding from Senator Ted Stevens. The project gained momentum through the dedicated efforts of longtime state legislators from the region, including Representative Bryce Edgmon of Dillingham and Senator Lyman Hoffman of Bethel, with strong local support. This collaborative effort culminated in an appropriation of $20 million from the Alaska Legislature in 2008. Numerous Aleknagik mayors also played a significant role in maintaining the momentum for the bridge, securing legislative support, and garnering backing from the Alaska Department of Transportation (AKDOT). The Wood River Bridge ultimately became a successful project, enjoying widespread support [6].

Information about the model

1384 images were taken by a UAV-based Sony ILCE-5100 camera from an average altitude of 11.7 meters, achieving a ground resolution of 1.4 mm/pixel over a 618 square meter area.  Agisoft Metashape Professional software version 2.0.2.16334 was used to create the resulting photogrammetry model on a Windows 64 bit OS, with 63.68 GB of RAM, an 11th Gen Intel Core i9-11900 CPU, and an NVIDIA GeForce RTX 2060 SUPER GPU. Out of 711,700 possible points, 453,315 were successfully matched with an RMS reprojection error of 0.254447 m. The mean key point size was 4.51811 pixels. No key points were used, and the average tie point multiplicity was 9.05. High accuracy alignment parameters were chosen with generic preselection enabled, but without reference preselection. The limits were set to 40,000 key points, 1,000 per Mpx, and 4,000 tie points. Stationary tie points were excluded, without guided image matching or adaptive camera model fitting. The matching time was 27 minutes and 12 seconds, using 6.47 GB of memory. The alignment process took 40 minutes and 34 seconds, using 2.21 GB of memory.

References