Remote sensing enables monitoring of transportation infrastructure across seasons and across the world. Above is an example of an interactive map made using Landsat 7 satellite images of Eastern Estonia. Landsat 7 captured the summer image, at left, in July 2002. We recently wrote about the algae bloom and ship traces visible in this image. The image on the right corresponds to the following winter 2002-2003.
Ice Roads. In the winter the sea can freeze enough to allow car traffic. In the case of Estonia, ice roads are set when ice thickness surpasses 22 cm (8.7 in) thickness. These ice roads have special regulations like no stopping, minimal spacing between cars, and avoiding certain speed ranges that would resonate with water waves underneath. When the snow is plowed away, the bare ice becomes thicker than the surrounding areas, delaying springtime melting. This blocks light longer, modifying algae growth.
Ferry. The Tuule Grupp 25 minute ferry connection between Virtsu and Kuivastu is kept open during winter using ice breaker ships. The summer image shows the Ferry midway through one of its crossings. The winter image shows the corridor free of ice as the icebreaker ships crosses several times per day.
Regional Harbor. The Port of Parnu is an important regional harbor serving the southwestern Estonia hinterlands, which provide much of the raw materials exported through Estonian ports. The port cuts an open corridor in winter using Ice breakers.
This is just an example of how remote sensing can be used to monitor and gather qualitative information. With more cadence of images, increased resolution or video capabilities, it could be possible to extend its potential into quantitative dynamics: When and how is the ice freezing and melting, how often are ice breakers working or how much traffic is using each infrastructure type.
Images were taken from USGS repository for Landsat 7, processed to surface reflectance, styled in TileMill, hosted on Mapbox and embedded using mapbox.js. Clear winter images are harder to get since winter at high latitudes only has a few hours of daylight. Winter raster actually corresponds to early Spring (March 29) which for Estonia still means ice season.