As of 1 August 2017, the KCCI-TV SchoolNet Project was discontinued. This website will eventually go away as well. Thanks for your usage over the years since 2002! Questions? akrherz@iastate.edu

Select Lesson:

8. Orthophotography

Objectives:

The goal of this lesson is to show how to use the Orthophotography that is available on the website. Orthophotos are simply images that have been processed to remove any disortion caused by terrain effects in relationship to the camera. Think about taking a picture of the mountains from an airplane. The differing heights of the mountains will cast shadows on your image. Orthophotography tries to remove these distortions. You have probably seen these images used on National TV during Iraq coverage to show areas of the country from above.

SchoolNet8.com Online Resources:

Currently, only one application uses the Orthophotos that are available for the state of Iowa.

The functionality on this page is hopefully straight forward. You can select your SchoolNet8 site, a resolution of the image, and an image size. Larger image sizes will require longer times to download.

Questions:

  1. Asphalt and concrete readily absorb the sun's energy during the day and release it as heat during the afternoon and evening. Take a look at a shot of the SchoolNet8 site at Ankeny Christian Academy. How might the school's surroundings affect the temperatures recorded there?
  2. The northern half of Iowa was scoured nearly flat by glaciers during the last ice age. As a result, the topography there offers little to resist the often windy conditions that affect the northern plains. Look at 5-meter-resolution pictures of the Schoolnet sites in Farnhamville and Boone. How might the land surrounding the sites affect the winds measured there?
  3. Hills, buildings, and trees surrounding a SchoolNet8 site might make the wind speeds and gusts recorded by a site seem less than they actually are for the surrounding area. The scientific term for this would be that the site is not representative of the greater area. Look at a 1-meter resolution picture of our site at Oskaloosa Christian school. How might the site's surroundings affect the winds recorded there?
  4. Crops such as corn and beans release a great deal of moisture into the air during the growing season through a process called evapotranspiration. This can create unrepresentatively high dewpoint and humidity readings to be recorded by a weather station. Take a look at 2-meter resolution ortho photography of our site at Rockwell City. How might the readings at the school on a summer day with southerly winds be affected by its surroundings?

Possible Answers:

  1. Urban areas absorb and retain a greater amount of the solar radiation received than rural areas do. This phenomena is referred to as an urban heat island. The effects are increased temperatures during the day and night, particularly on sunny days. The effect is more pronounced for the larger cities than small towns. Cities like Des Moines function as urban heat islands quite often.
  2. In general, wind will flow faster when faced with fewer obstacles. So in the rural and flat areas of Iowa, the winds would be able to blow faster than in urban and forest areas.
  3. There are numerous trees in the area which would tend to resist the wind flow and cause the SchoolNet8 site to record weaker winds than what are prehaps observed outside of town.
  4. The large field just to the south of the SchoolNet8 site will increase humidities during the growing season due to evapotranspiration. The fields on the other sites of the school will probably affect humidities as well.

Other Educational Resources: