Aerial Photo Scales

Scale of a Vertical Aerial Photo (From Paine Chapter 4 With Elements of Arnold Ch. 1)

Scale Classification

Small Scale

1:24,000 and smaller
Medium Scale 1:10,000 to 1:24,000
Large Scale 1:1,000 to 1:10,000
Very Large Scale

1:1,000 and larger

Some useful Scales in Forestry:

1:15,840  1 inch = 20 chains         1:7,920    1 inch = 10 chains

Note: Large scale and Small scale are only relative terms.

For aerial photos or maps of a given area:

  • Large scale shows greater detail but a smaller area.
  • Small scale shows lesser detail, but a larger area.

Comparing different scales is linear. A given distance on the ground will be twice as long at 1:25K as it will at 1:50K.


Area relationships are squared. Map 1 is four times the area of Map 2 and sixteen times the area of Map 3.

Theory of Scale

Three analytical methods: RF, PSR and equivalent scale

Graphical scale, verbal scale

Representative Fraction (RF)
Ratio of a distance on the photo to the same distance on the ground
Expressed as simple fraction with 1 as numerator

4.2.2 Photo Scale Reciprocal (PSR)
The inverse of RF, also unitless
Take PSR of 24,000. Means the ground distance is 24,000 larger than the map distance (of the same unit)

If the PSR is small it is closer to the actual object size than if the PSR is large

4.2.3 Equivalent Scale
Showing map units as an equivalence in different ground units.
1:24,000 is the same is 1inch = 2,000 feet on the ground

Photo scale relates size or distance on the photo to actual size or distance on the ground. Scale needed to correctly interpret an aerial photo.

4.3 Types of Scale

Average scale – can refer to entire project, single photo, or portion of a photo. Usually not the exact scale of the photos due to various factors

Point scale – photo scale at a point on the ground at a given elevation

4.4 Variation in Scale

Two primary causes of variation over a single photo

  1. Tilt
  2. Differences in flying height above the ground caused by differences in ground elevation, or topography

Another source of variation between photos in the same mission comes from slight changes in height between exposures.

RF can also be defined as focal length divided by flying height above the terrain. Focal length constant, but flying height above the ground varies as elevation changes.

Higher ground elevations have a larger scale than lower elevations (See Figure 4.2)

Scale changes from point to point over the photo with topography and height of the airplane.

Ridge tops have a larger scale than valleys.

Average scale can vary among photos on the same project and be different than the project average scale.

Focal length of the camera affects photo scale. A cameral using a lens with a longer focal length increases the scale of the photo. (See Figure 4.3)

 Tilt: the scale of a tilted photo changes in a regular manner throughout the photo.

Scale changes across the photo in the direction of the tilt. (See Figure 4.4)

If the scale near the center of the photo is approximately correct:

    The scale is smaller on the side of the photo positive that is tilted upward.

    The scale is large on the side of the photo positive that is tilted downward.

Basic scale equations

See Figure 4.5  Using similar triangles:

f = focal length, H or A-E = flying height above the ground, PD = photo distance, GD = ground distance. f and H have to be in the same units

Photo Scale Determination

Using the camera focal length and flying height equation is easiest

Can be done remotely. If we use the average elevation we get the actual scale. If we use a point elevation we get a point scale

Ways of getting the ground distance

  •     Measure the GD directly on the ground
  •     Measure the map distance and compute the ground distance using the map scale
  •     If we know the ground distance between two points only the photo distance is necessary
  •     Use GPS to get grid coordinates and calculate the distance. Which is better UTM or Lat-Long?

Can sometimes use section boundaries if working in an area where the Public Land Survey System is used.

Finding the Scale by Comparison

When the scale of the map or image is unknown or in question. Need another map of known scale to compare.

Locate the same two points on each map or image of a particular earth surface area.

  1. If using a vertical airphoto try to select points so that the line between them goes through the Principal Point (PP).
  2. Measure the straight-line distances as carefully as possible with an engineer’s scale. Insert the values into the equations.
  3. Solve the equation by cross-multiplication. The value solved is the denominator for the unknown RF

Line AB = distance from point A to point B on map of known scale.
Line A’B’ = distance between points A and B on the map or image of unknown scale.
D = denominator of known RF.
= denominator of unknown RF

4.6.1 Assumptions

All these methods assume a truly vertical photo. No simple way of determining tilt. Must rely on the skill and experience of the pilot.

Assumes error caused by topographic displacement when measuring the photo distance of the baseline is negligible. The error can be minimized by establishing the baseline as close to the nadir as possible and keep both ends of the baseline at approx. the same elevation (See Figure 4.8)

This page was originally hosted on Penn State PASS Space. I think I used Microsoft FrontPage.

Posted in FORT 230 | Leave a comment

Science means being skeptical

Where the ‘Wood-Wide Web’ Narrative Went Wrong

May 25, 2023 by Melanie Jones, Jason Hoeksema, & Justine Karst

Over the past few years, a fascinating narrative about forests and fungi has captured the public imagination. It holds that the roots of neighboring trees can be connected by fungal filaments, forming massive underground networks that can span entire forests — a so-called wood-wide web. Through this web, the story goes, trees share carbon, water, and other nutrients, and even send chemical warnings of dangers such as insect attacks. The narrative — recounted in books, podcasts, TV series, documentaries, and news articles — has prompted some experts to rethink not only forest management but the relationships between self-interest and altruism in human society.

But is any of it true?

The three of us have studied forest fungi for our whole careers, and even we were surprised by some of the more extraordinary claims surfacing in the media about the wood-wide web. Thinking we had missed something, we thoroughly reviewed 26 field studies, including several of our own, that looked at the role fungal networks play in resource transfer in forests. What we found shows how easily confirmation bias, unchecked claims, and credulous news reporting can, over time, distort research findings beyond recognition. It should serve as a cautionary tale for scientists and journalists alike.

First, let’s be clear: Fungi do grow inside and on tree roots, forming a symbiosis called a mycorrhiza, or fungus-root. Mycorrhizae are essential for the normal growth of trees. Among other things, the fungi can take up from the soil, and transfer to the tree, nutrients that roots could not otherwise access. In return, fungi receive from the roots sugars they need to grow.

As fungal filaments spread out through forest soil, they will often, at least temporarily, physically connect the roots of two neighboring trees. The resulting system of interconnected tree roots is called a common mycorrhizal network, or CMN.

When people speak of the wood-wide web, they are generally referring to CMNs. But there’s very little that scientists can say with certainty about how, and to what extent, trees interact via CMNs. Unfortunately, that hasn’t prevented the emergence of wildly speculative claims, often with little or no experimental evidence to back them up.

One common assertion is that seedlings benefit from being connected to mature trees via CMNs. However, across the 28 experiments that directly tackled that question, the answer varied depending on the trees’ species, and on when, where, and in what type of soil the seedling is planted. In other words, there is no consensus. Allowed to form CMNs with larger trees, some seedlings seem to perform better, others worse, and still others seem to behave no differently at all. Field experiments designed to allow roots of trees and seedlings to intermingle — as they would in natural forest conditions — cast still more doubt on the seedling hypothesis: In only 18 percent of those studies were the positive effects of CMNs strong enough to overcome the negative effects of root interactions. To say that seedlings generally grow or survive better when connected to CMNs is to make a generalization that simply isn’t supported by the published research.

Other widely reported claims — that trees use CMNs to signal danger, to recognize offspring, or to share nutrients with other trees — are based on similarly thin or misinterpreted evidence. How did such a weakly sourced narrative take such a strong grip on the public imagination?

 

 

Support Undark Magazine

Undark is a non-profit, editorially independent magazine covering the complicated and often fractious intersection of science and society. If you would like to help support our journalism, please consider making a donation. All proceeds go directly to Undark’s editorial fund.

 

 

We scientists shoulder some of the blame. We’re human. Years ago, when the early experiments were being done on forest fungi, some of us — the authors of this essay included — simply got caught up in the excitement of a new idea.

One of us (Jones) was involved in the first major field study on CMNs, published more than 25 years ago. That study found evidence of net carbon transfer between seedlings of two different species, and it posited that most of the carbon was transported through CMNs, while downplaying other possible explanations. This is what’s known as “confirmation bias,” and it is an easy trap to fall into. As hard as it is to admit, it was only due to our skepticism of the recent extraordinary claims about the wood-wide web that we looked back and saw the bias in our own work.

Over decades, these and other distortions have propagated in the academic literature on CMNs, steering the scientific discourse further and further away from reality, similar to a game of “telephone.” In our review, we found that the results of older, influential field studies of CMNs have been increasingly misrepresented by the newer papers that cite them. Among peer reviewed papers published in 2022, fewer than half the statements made about the original field studies could be considered accurate. A 2009 study that used genetic techniques to map the distribution of mycorrhizal fungi, for instance, is now frequently cited as evidence that trees transfer nutrients to one another through CMNs — even though that study did not actually investigate nutrient transfer. In addition, alternative hypotheses provided by the original authors were typically not mentioned in the newer studies.

As these biases have spilled over into the media, the narrative has caught fire. And no wonder: If scientists themselves could be seduced by potentially sensational findings, it is not surprising that the media could too.

Journalists told emotional, persuasive, and seductive stories about the wood-wide web, amplifying the speculations of a few scientists through powerful storytelling. Writers imbued trees with human qualities, portraying them as conscious actors using fungi to serve their needs. Fantasy moved to the foreground, facts to the back. In an odd kind of mutual reinforcement, the media blitz may have convinced experts in other subfields of ecology that the claims about CMNs were well-founded.

The episode underscores how important it is for journalists to seek out a broad range of expert opinions, and to challenge us scientists when our assertions aren’t clearly backed up by rigorous research. By directly asking scientists questions such as “What other phenomena could explain your results?” and “How many other studies support this hypothesis?” journalists may be able to better understand and convey some of the uncertainty around scientific conclusions. The best science writing can capture the hearts and minds of the public, but it must be true to the evidence and the scientific process. If not, the consequences can be far-reaching, affecting policy decisions that impact real people.

There are many captivating and scientifically well-grounded stories we can tell about fungi in forests — and we should. Mycorrhizal fungi underlie many of our favorite edible mushrooms, including truffles, chanterelles, and porcinis. And some herbs in the understories of forests, rather than photosynthesizing sugars like a normal plant, use CMNs to connect to trees and steal their sugars. Forests are fascinating places, marked by a rich diversity of interactions between plants, animals, and microbes. The stories are endless. We just have to tell them with care.


 

Melanie Jones is a professor in the Biology Department at the University of British Columbia’s Okanagan campus. She and her students have been studying mycorrhizal fungal communities in forests, clearcuts, and wildfire sites in British Columbia for 35 years.

Jason Hoeksema is a professor in the Department of Biology at the University of Mississippi. His research addresses a diversity of questions regarding the ecological and evolutionary consequences of species interactions on populations, communities, and ecosystems.

Justine Karst is an associate professor in the Department of Renewable Resources at the University of Alberta. She has been studying the mycorrhizal ecology of forests for 20 years.

 

This article was originally published on Undark. Read the original article.

Posted in Uncategorized | Leave a comment

What to do with the new AI tools

I follow this writer on Twitter. He has some good examples of using the new AI chatbots.

Posted in Uncategorized | Leave a comment

Goodbye Pass Space

A few weeks I got an email that Penn State Pass Space would be leaving next year and they noticed that I was still using it. Then I got a message from my local IT staff. So the old web space on Pass will no longer be available. So this will be it for personal web space. I spent a lot of time developing my web page on Pass and training students to use it.  we used Microsoft Front page. All my web pages on Pass are structured by Frontpage, too. WordPress is good though, and I am looking forward to using it into the future.

We also had a few years using Typeface, which was dropped for WordPress.

Posted in Observations | Tagged | Leave a comment

Satellite imagery for studying smoke effects

This article from September, 2020 describes uses of satellite imagery to study the spread of smoke from wildfires. It showed the GOES West satellite to show fires in Oregon. GOES is the commonly used weather satellite. It has a low resolution and covers the entire hemisphere in a number of electromagnetic bands to emphasize clouds and water in the atmosphere.

https://www.pennlive.com/news/2020/09/satellite-view-of-earth-puts-wildfire-smoke-in-perspective-and-its-huge.html 

I am certain that this year, 2021, will show even more extensive smoke due to the greater number of wildfires.

Posted in FORT 230 | Leave a comment

Mont Alto Monuments Map

I will be using this to demonstrate how changes to the map in ArcGIS Online will work in an embedded map. It takes a few minutes for the PEMA imagery to come over.

 

Posted in FORT 230, FORT 260, Uncategorized | Tagged , , | Leave a comment

Color Comparison 2020

Posted in Uncategorized | Leave a comment

Study Sites for Fall 2020

This year we weren’t able to visit the sites in person. We looked at previous imagery and ground photos and discussed the attributes of each site. We will make maps of the areas in subsequent labs.


Posted in Uncategorized | Leave a comment

Volcanos, Aerosols, and the Roman Empire

A recent article in Physics Today links the eruption of a volcano on Umnak Island in Alaska to agricultural failure in the Roman Empire and the assassination of Julius Caesar in 44BCE. The millions of tons of aerosols sent into the atmosphere led to cooling and then the failure of the Roman crops. The unrest may have led to the assassination of Julius Caesar, who was the ultimate ruler at the time. Follow this link to see details.

Posted in Uncategorized | Leave a comment

Remote Learning

I got this from Twitter.

 

Posted in Uncategorized | Leave a comment