Resection vs Intersection navigation, what's the difference?

Summary

This video explains the difference between resection and intersection in navigation. Resection involves finding one's own location on a map by taking bearings from two identifiable features. Intersection, on the other hand, is used to pinpoint another's location by taking bearings from two known points. The presenter demonstrates both techniques using various compasses and emphasizes the UK's Ordnance Survey maps for their detail. The video concludes with the importance of sharing coordinates for precise location sharing.

Takeaways

• 📍 The difference between resection and intersection is that resection is used to find your own location on a map, while intersection is used to find someone else's location.
• 🧭 Both techniques involve taking bearings from two or more features and plotting them on a map to find the point of interest.
• 🌟 The video demonstrates the process of resection using two compasses, a Brunton True Ark 20 Luminous and a Kanga 38, both American compasses.
• 🏞️ For resection, the user identifies two visible and identifiable features on the ground and on the map, such as a trig point and a wall junction.
• 📐 The user takes bearings to these features and plots them on the map, with the intersection of the lines indicating the user's location.
• 🔢 The user can share their location using UK grid references, UTM coordinates, or military grid reference system (MGRS).
• 🔄 The video also covers the intersection technique, which requires bearings from two known locations to pinpoint a point of interest.
• 🗺️ The Ordnance Survey maps in the UK are praised for their detail, making them ideal for such navigation techniques.
• 📐 In the demonstration of intersection, the user uses a Suunto A30 compass to take a bearing from a point of interest and then walks to another location to take a second bearing.
• 📊 The user plots the bearings on the map, and the intersection gives the exact location of the point of interest.
• 📝 The video concludes by emphasizing the practicality of both resection and intersection for sharing precise locations with others.

Q & A

What is the main difference between a resection and an intersection as described in the video?

A resection is the process of finding one's own location on a map using two or more bearings from identifiable features. An intersection, on the other hand, is used to find the location of something else on a map by taking bearings from two known locations.

What are the two compasses used in the demonstration for the resection technique?

The two compasses used are a Brunton True Ark 20 Luminous, an American compass, and a Kanga 38, which is also an American compass.

What is the significance of the UK grid reference mentioned in the video?

The UK grid reference is a system used to specify a location within the United Kingdom to a high degree of accuracy. It can be used to communicate one's location to within 100 meters or even 10 meters with additional precision.

Why is the magnetic declination mentioned in the video, and how does it affect the bearings taken?

Magnetic declination is the angle between magnetic north and true north. It is mentioned because it can affect the accuracy of bearings taken with a compass. However, in the video, the declination is only 13 minutes west, which is a small enough adjustment that the presenter chooses not to account for it in this case.

What is the purpose of taking bearings to a wall junction and a trig point in the resection example?

The purpose is to identify two fixed, identifiable points on the ground that can also be located on the map. By taking bearings to these points, the intersection of the lines on the map can help determine the user's location.

What is the UTM coordinate system, and how is it used in the video?

The Universal Transverse Mercator (UTM) coordinate system is a method of assigning locations on the Earth to a grid using a series of zones. In the video, the presenter uses UTM coordinates to communicate their exact location on the map.

What is the purpose of the intersection technique demonstrated in the video?

The intersection technique is used to identify the location of a point of interest on a map by taking bearings from two known locations and finding where the lines of these bearings intersect on the map.

Why does the presenter use different compasses in the video, and what is the significance of their origin?

The presenter uses different compasses to demonstrate that they are not limited to using silver compasses, as was asked in a previous Q&A session. The origin of the compasses is mentioned to highlight the variety of tools available and to correct a misconception.

What is the importance of the Ordnance Survey map mentioned in the video?

The Ordnance Survey map is highlighted for its detailed and accurate representation of the landscape, which is crucial for accurately locating points on the map using the intersection technique.

How does the presenter locate a point of interest using the intersection technique in the video?

The presenter locates a point of interest by taking bearings from two different vantage points to the same distant feature, then plotting these bearings on the map. The intersection of these bearings indicates the location of the point of interest.

What is the Military Grid Reference System (MGRS) mentioned in the video, and how is it used?

The Military Grid Reference System (MGRS) is a geocoordinate standard used by NATO for locating points on the Earth. It is used in the video as an alternative way to communicate a precise location, similar to the UK grid reference or UTM coordinates.