Hi fellows,

We have some queries to answer some technical issues regarding solar observation to compute/obtain azimuth of an observed station and how convergence angle applied to the computation of grid azimuth.

1. What is the azimuth reference computed from a solar observation?

2. How to apply convergence angle when the observed stations is in the left or right in the central meridian and how it differ from each other? 

3. What is the difference between true north, grid north and magnetic north?

4. What is the  azimuth reference used in executing a traverse for a meridional block survey?( Meridional blocks are defined by each geographic coordinates and later converted to grid coordinate.)

Thank you fellows.

Find Similar Content by Clicking These Tags ☟
Subject Tags: azimuth, observation, solar, surveying

This Content Originally Published to Land Surveyors United Network

Views: 1555

☇ Reply to this

Replies to This Discussion

Are you familiar with a  document titled " Astronomical Observation Handbook" by Charles Ghiliani? It describes the techniques a surveyor needs to know for determining azimuths, north, etc using astronomic observations. If you send me your email address I can send you the pdf. It's only about 17 pages long.

Please send me the PDF . Much obliged Arthur Will

Here's the document.

Download Survey Documents-Members Only

PLEASE SIR  SEND IT IN PDF FORM

Here's the document.

Download Survey Documents-Members Only

Hi Carlos, i saw your mail regarding the document, and it is an important helpful document. I kindly ask if it is possible to email the document to me as well. my email _ jaolbosaj1@gmail.com

 

Thank you

Here are the two relevant documents.

Download Survey Documents-Members Only

Here are the two documents discussed.

Download Survey Documents-Members Only

Hi Carlos, maybe that would be helpful document. Please send at josephjerneyuy@yahoo.com. Thank you bro.

Separately, I sent you the document I originally noted. I just located another paper in my files on Astronomic Geodesy, which I am attaching here, and maybe provides more help.

Download Survey Documents-Members Only

It's been 30+ years since I last did one, so I will defer to the instructions provided by others.  I will however tell you that the results we got were very impressive. 

We had a 25 mile Geodetic control Survey in Upstate NY in early 80's.  One of our party members was from Ghiana, (British Scholl of Survey), so if I remember correctly they could not observe Polaris or Southern Cross as they were so close to the Equator.

In any case he had a program in his TI 59 that we used.  We scaled a lat/long from a quad and used a Radio Shack time cube (remember them?) and used a T2 and Rolffs solar prism.  We observed azimuths on 4-5 of our legs that were adjusted from the 25 mile Geodetic traverse.

The results on the Solar vs. conventional were all with less than 10 seconds of the adjusted conventional control.

Pretty neat stuff.

Let us know how you make out. 

Hi,

In brief terms Astronomic azimuth is true north; your meridional circuit is grid north, and magnetic north is the local magnetic north at any point on the earth's surface (not very useful in surveying terms but alas it is used as a reference in Australia for their cadastral surveys>>baffling!!)

True North and Grid North are related by convergence..Be very careful applying the correction you will need to draw a diagram..

At the central meridian of your grid system (meridional circuit) by definition grid bearings = astro bearings; and as we move east or west of this CM the convergence increases + or - depending on whether we go west or east.

You are in the Northern Hemisphere I take it so the convention is:

West of CM: Grid > True

East of CM: Grid < True

Southern Hemisphere:

West of CM: Grid < True

East of CM: Grid > True

To see this you will need to draw a diagram with pole (North or South depending on hemisphere), and draw location of observer P and a direction to a point say 'A'. Grid North or South is a line parallel to CM line (a meridian by definition), and True North or South the direction to the pole for the observer.

Remember that depending on the map projection you are using a different calculation of convergence may be needed but for a TM the general approx formula is:

Conv = dLong * SIN (Obs Latitude)

A scaled position of observer's LAT / LONG will be necessary to get a good approximation of the convergence at any point.

Hope this helps a bit

Grant

RSS

Global Trade organization for Professional Land Surveyors and Geospatial Pros. Frictionless GeoCollaboration Surveying Forum and Groups

Surveyor Hubs and Tags

Surveyor Community Hubs For World Regions

Surveying Hubs For US States

Social Support For Equipment

Surveying Photos by Tag

Surveying Videos by Tag


Share on Tumblr
+ Surveyor Sharer

Drag Button to bookmark bar and view submitted links here.Will soon be moved to a directory

What You Missed

Kevin Smith promoted Kyle's profile
2 hours ago
Dirty Jersey posted photos
2 hours ago
Dirty Jersey promoted Dirty Jersey's photo
2 hours ago
Ye Yint promoted Anel Hadzic's photo
3 hours ago
timothy cox updated their profile
4 hours ago
Profile IconJUMA JACOB, Kevin Smith, Jai and 3 more joined Land Surveyors United ::
4 hours ago
Matt Gardner's discussion was featured

Surveying techniques

Hey all, just online catching up on some industry insights when i found this so I thought someone…See More
5 hours ago
Surveying Jobber commented on Cody Baertschi's blog post Surveying in an Inhospitable Environment: Grassy Lake, Arkansas
"awesome post... thanks for sharing!"
5 hours ago
Surveying Jobber promoted Cody Baertschi's blog post Surveying in an Inhospitable Environment: Grassy Lake, Arkansas
5 hours ago
Cody Baertschi was featured
5 hours ago
Dirty Jersey's photo was featured

Surveyor being Punished

Surveying trouble
5 hours ago
sanju s rathod's discussion was featured

Cross Section Maker

This program is a plot of the cross section Excel to Autocad.For any help, mail me:-…See More
5 hours ago
Cody Baertschi's blog post was featured

Surveying in an Inhospitable Environment: Grassy Lake, Arkansas

Click the link to read about the efforts of my company to handle an intricate survey in a delicate…See More
5 hours ago
Paul Quagge's discussion was featured

Survey Cad Software

Hello Fellow Surveyors,I'm putting a survey business together doing boundary and topo and am on a…See More
5 hours ago
talat promoted sanju s rathod's discussion Cross Section Maker
6 hours ago
talat replied to sanju s rathod's discussion Cross Section Maker
"PlotCross section2015.xla file is not opening."
6 hours ago
Валентин Панчук posted a photo

GNSS from Ukraine

I like my job
10 hours ago
Arnel M. Domag replied to pasha's discussion precise station in survey work
"0.6mm? Less than 1mm?"
13 hours ago
LSU Justin's group was featured
Land Survey Media Thumbnail

Female Land Surveyors

Female Land Surveyors need each other's support. If you are a female land surveyor, join this group…See More
16 hours ago

Take This Page With You

follow us in feedly

Take this Page With You

QR Code for This Page: What is this?

Surveyor Support

Get Started Guide

Network Feedback

Send Us a Tip

Questions Comments

Help Keep Us Free



© 2015   © Created by Land Surveyors United

Badges  |  Contact LSU  |  Privacy Policy  |  Terms of Service

Related Posts for Land Surveyors UnitedRelated Posts Plugin for Land Surveyors United Network ForumRelated Surveying Photos Land Surveyors United Live Support