Using Software Bidding Gravity Magnetics Electrical Seismic Lecture segment		U s e r  A d v i c e Use the classifications at the left to jump to a general group of questions. No link means no questions answered yet! Alternatively, use the browser's "Find" function to look for a keyword. Don't forget to keep searching if the first occurrence isn't your question answered. (This is a good tip in the Note Outline pages, too, to find a topic quickly.) Use Back in the navigation bar of your browser to return to your place in the site, or use the buttons below to jump to the top level of each module. Links to other pages or other parts of this page are underlined in this file.   F A Q s If you have a question which isn't answered here, email it to me at thomas@unimelb.edu.au. If the same question comes in frequently, I'll add it to this page (with an answer). If you have a better answer than you find here, email that to me, too! and I'll replace the answer with yours (and an acknowledgement). Question: I have a computer at home. Can I work on this subject there? Answer: Sure, particularly if you have an internet connection, so that you can log on to this site. There is no need to come to the scheduled class unless you need more help, and I hope you won't! You can also work at any of the public computer sites around the campus. Talk to the manager of the individual site about access. Question: Is this subject just lectures and computer work? Is there any fieldwork? Answer: Well, no, no fieldwork within the assessable components. There will be a VIEPS Honours/Masters field camp within the coming year, which you could attend (it could form part of your Honours coursework component, if you do that). We may have some equipment demonstrations during the tutorial sessions, later. Question: What will happen in the tutorial sessions? Answer: I don't know, yet. I will be available for questions, we may have demonstrations of computer software, either for the subject or in Geophysics, and the occasional visiting speaker. I hope to be responsive to student requests as far as possible.
Intro to GP		Gravity	Magnetics	Electrical	Seismic

Software usage 

Bookmarks	Question: How can I return to where I left off in the site? Answer: Bookmark (in the menus Bookmark - Add Bookmark) when you leave, and pull down the menu to find that bookmark when you return. If using a public computer this may not survive, so write down the URL of the last page and type that in the address bar when you start up.
Spreadsheets	Question: I know nothing about spreadsheets! What can I do? Answer: If you have access to a computer with a spreadsheet installed, (Microsoft Excel is most likely, or one of the integrated applications which usually have "works" in the title) look around the hard disk or source files for a tutorial - and work through it. The idea of a spreadsheet is the first step; after that you can use the online help,or manual, to guide you on more specific questions. I'm developing some material on a separate page, including sample sheets.
Downloads	Question: How do I download data from the site? Answer: Hotlinks, here and elsewhere, will be underlined and/or in bold type - see the "Back to top" phrase on the left. As you roll your cursor over a hotlink, the status bar at the bottom of your browser will tell you what kind of link it is - an email address, another page, or a data file (usually with the .dat extension). Clicking on the link starts the transfer process - Windows will ask where to put the file, usually, and Mac OS will put it into a folder preset under the preferences menu.
Acrobat (.pdf) files	Question: What is a ".pdf" file? What is an "Acrobat" file? Answer: Adobe Corporation has constructed a method of printing computer documents to file so that they can be read by an Acrobat Reader application on a wide variety of computer platforms, and appear in all of their original glory. The files usually have the extension ".pdf" (for Portable Document Format). Generally such files cannot be altered, but they can be printed and often copied. They can be indexed and can have hotlinks embedded... If your computer does not have the Acrobat Reader, go here to download a copy. It's free. If you wish to know more about Acrobat Reader, here is a tutorial.
Saving text files Controlling decimal places	Question: How do I save my calculated results as a "text file"? How do I control the precision (or number of decimal places) in the result? Answer: Assuming that you are working in a spreadsheet like Microsoft Excel... First, make sure that you have saved the workbook with your calculations in it as an Excel file (with a .xls extension, for instance). Then you can come back to it later. Show the page which you want to save as text. To control the appearance of the result, highlight the column or range you want to change, and go to the menu Format - Cells item. Selecting Number discloses a control for the number of decimal places. If you want different formats, investigate this menu item further, and use the On-lineHelp. Having organised this, go to menu item File - Save As, enter a new name for the new file (perhaps with a .dat or .txt suffix) and choose "Text (Tab delimited)" from the drop-down menu. The Application will ask several times whether you want to do this, because it does mean abandoning the formulae, but you've already saved those in the original file, haven't you! The file now should open in editors or wordprocessors as well as Excel. PS Java has difficulty reading scientific notation. Use fixed-decimal place format for data which is being sent to a Java applet.

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Bidding 

	Question: What is the basis for my bid? Answer: Read the RFB page to find out what the problem is. If you are confident you know how to do the data acquisition, work out the various details and cost them out, so that you end up with the station spacing and data quality you need. If you don't know how to do this, go back to the simulation pages and see what happens as you change these parameters.
	Question: Can you be more specific? How do I know the station spacing, for instance, or how often to return to base? Answer: Well, you could guess! You could also ask me to tell you the answers - but after this year you have to pay a consultant to do that, and it wouldn't be why you were employed! The site is intended to help you reach these conclusions yourself. In the Survey Design page, you can experiment with different settings of the acquisition parameters, and decided for yourself whether you would see a deep or shallow target with those settings. (Click on the Java buttons to experiment with different targets.) In the Observational Errors page you download small datasets which you can experiment with, to find out the effect of changing the base station repeat time, for instance. So, working through the questions you need to answer before putting in your bid, you should look at the rest of the site to see where the answers lie.

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Gravity 

Gravity tides	Question: Do gravity tides change from place to place like ocean tides? Answer: Yes, although they are not as dependent on local topography. Tidal calculations do depend on latitude and longitude, and the actual amplitudes are affected by (frinstance) distance from the edge of the continent, which affects the flexure of the crust/

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Magnetics 

The airborne option	Question: Could we do airborne magnetics for this problem? Answer: Well, yes. Some companies will now offer down to 10m terrain clearance surveys, even with fixed wing aircraft - but it isn't likely that would be an option on near-urban areas. In any case the area involved here is quite small, and you will work out the cost of acquiring comparable data by foot.
USGS Magnetics Branch	Question: I can't open the USGS Magnetics site? Answer: It appears to be offline. In order to remove the regional field, start with the following values at the corners of the survey area: 3.8 0.7 -2.7 -0.3 NW NE SE SW These are approximately equal to the regional values, with a constant value of the order of 51350 nT removed.

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Electrical methods 

	Question: Is resistivity the only electrical method to use here? Answer: No, but it is the most straightforward and interpretation is simplest. Electromagnetic methods could also be used (look that up in Reynolds) but the inversion algorithms are notably more complicated.

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Seismic methods 

	Question: What about the guy sitting next to the source explosion? Answer: He(?) is a fool. Explosives are safe if treated with respect, but the Earth is a non-homogeneous medium and staying clear is a sensible precaution. A good tip is to stand at least as far away as the shotfirer, who usually has to be trained to get a licence, so knows how to minimise the risks.

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Lectures 

	Question: Why don't the lectures cover the same material as the website? Answer: Geophysics is a big field, and I hope that the two inputs are complementary. The website gives hands"on" experience; the notes and the lectures may give a framework for organising some of that experience.

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