# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Re: Errors in online version of HO249**

**From:**Gary LaPook

**Date:**2007 Nov 29, 11:04 -0800

Gary LaPook adds: Here is my reply to Mr. Doherty: Dear Mr. Doherty, Thank you for your reply. I know that it is very rare that a navigator would use altitudes near zero so it is not surprising that the error was not discovered sooner. I found it when I was testing a method for computing Hc and was comparing my results with H.O 249 to ensure that method I was testing was working. As part of the test protocol I tested cases near zero and, at first, couldn't figure out why my results didn't match, assuming there was a problem with my method. Only then did I notice the discrepancy in H.O. 249. This also caused me concern that there might be other errors in H.O. 249 that were not so apparent. Hopefully your review has eliminated this concern. Gary LaPook On Nov 29, 10:53 am, glap...---.net wrote: > Gary LaPook writes: > > I recieved the following email from the government website tha had > published H.O 249 with errors. > > "Mr. LaPook > > Thank you for bringing this error to our attention. It seems that the > Sight Reduction Table generation code improperly formatted entries > beginning with -0, inserting 00 instead. > > I am in the process of manually updating the electronic publications, > which will be posted to our Web site in the very near future. > > The errant publications were originally produced and posted to our Web > site in 1999. Which mean that, in their 8+ years of service, you are > the first and only user to notice the error! > > Regards, > > Tim Doherty > Office of Global Navigation/Technology > National Geospatial-Intelligence Agency > (301)227-1075 > > -----Original Message----- > From: Gary J. LaPook [mailto:garylap...---.net] > Sent: Wednesday, November 28, 2007 4:26 AM > To: Webmaster_NSS > Subject: Errors found in HO 249 > > Dear Sir: > > Quite by chance I noticed an error in the on line edition of HO 249 > volume 2. I then looked for similar errors and found that there is a > systematic error in both volumes two and three. For example, on page 5 > of volume 2 covering latitude 0� in the first column covering > declination of 15� at LHA 89 the altitude given is 00-58'; for LHA 90 > the altitude is given as 00-00'; and for LHA 91 the altitude given is > 00-58' which is the same value as given for LHA 89! This is > mathematically impossible. The problem is that the altitude for LHA 91 > should be negative 00-58'. The systematic error found all across the > tables up to at least latitude 39� is that all of the last positive > altitudes tabulated should all be negative altitudes! This is also > true for the values given for contrary name declinations. For example > on page > 163 of volume 2 covering latitude 27� in the first column for 0� > declination tabulated for LHA 91 an altitude of 00-53'; for LHA 90 an > altitude of 00-00'; and again at LHA 89 an altitude of 00-53'. The > altitude for LHA 91 should be negative 00-53'. > > I compared these examples with my printed copies of these tables > printed in 1970 and these errors do not appear in the printed version > which correctly label these altitudes as negative altitudes. > > Sincerely > > Gary LaPook > > On Nov 28, 1:33 am, glap...---.net wrote: > > I recently posted a link to the government web site where you can > > download copies of navigational publications including H.O 249. I > > quote below the email I sent to that site: > > > "Dear Sir: > > > "Quite by chance I noticed an error in the on line edition of HO 249 > > volume 2. I then looked for similar errors and found that there is a > > systematic error in both volumes two and three. For example, on page 5 > > of volume 2 covering latitude 0� in the first column covering > > declination of 15� at LHA 89 the altitude given is 00-58'; for LHA 90 > > the altitude is given as 00-00'; and for LHA 91 the altitude given is > > 00-58' which is the same value as given for LHA 89! This is > > mathematically impossible. The problem is that the altitude for LHA 91 > > should be negative 00-58'. The systematic error found all across the > > tables up to at least latitude 39� is that all of the last positive > > altitudes tabulated should all be negative altitudes! This is also > > true for the values given for contrary name declinations. For example > > on page 163 of volume 2 covering latitude 27� in the first column for > > 0� declination tabulated for LHA 91 an altitude of 00-53'; for LHA 90 > > an altitude of 00-00'; and again at LHA 89 an altitude of 00-53'. The > > altitude for LHA 91 should be negative 00-53'. > > > "I compared these examples with my printed copies of these tables > > printed in 1970 and these errors do not appear in the printed version > > which correctly label these altitudes as negative altitudes." > > > Sincerely > > > Gary LaPook --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To unsubscribe, send email to NavList-unsubscribe@fer3.com -~----------~----~----~----~------~----~------~--~---