# (American) Football question: measuring for a first down **URL:** \ **Category:** Factual Questions\ **Created:** [October 30, 2004, 9:55pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075 "2004-10-30T21:55:18Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![sixor9](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@sixor9](https://boards.straightdope.com/u/sixor9)\ **Post date:** [October 30, 2004, 9:55pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/1 "2004-10-30T21:55:18Z")
How do they keep the chains straight? Do they just have two markers exactly 5 yards apart? I assume there is at least one marker on the chains that indicates where the chains cross a 5 yard marker so that when they bring the chains on the field they have more than just a “guesstimate” of where the original line of scrimmage was. Is this true? ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [October 30, 2004, 10:42pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/2 "2004-10-30T22:42:59Z")
10 yards apart. Yes, there is usually a clip on the chains to mark a five yard line - you will notice when they bring the chains out to the field for a measurement that the official goes to the sidelines and carefully picks up the chain where it crosses a five yard marker so that he can plant that same spot on the chain on the line in the middle of the field. As for keeping them straight, they just eyeball it. A few degrees won’t actually make that much difference - sin(85 degrees) is about .996. One of the more endearing features of the game is the chain being used to determine that the ball needs to move 3 more inches when the placement was simply a judgement call by an official, and can probably be regarded as accurate to no closer than half a foot at best. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [October 31, 2004, 12:35am UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/3 "2004-10-31T00:35:29Z")
> [@yabob](#): > > One of the more endearing features of the game is the chain being used to determine that the ball needs to move 3 more inches when the placement was simply a judgement call by an official, and can probably be regarded as accurate to no closer than half a foot at best. Right, but once the official marks the placement of the ball that’s the “official” starting point. Just like balls and strikes in baseball. Once the umpire says “Strike!” it’s a strike even if the ball was actually low and outside. ---
**Author:** ![BobT](https://avatars.discourse-cdn.com/v4/letter/b/8e8cbc/32.png) [@BobT](https://boards.straightdope.com/u/BobT)\ **Post date:** [October 31, 2004, 9:00am UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/4 "2004-10-31T09:00:47Z")
Ahh, the first down measurement, one of football’s greatest shams! It purports to be extremely accurate when it really isn’t. It’s not that there usually is a clip on an intervening five-yard line. There’s always a clip. The problems in measurement have already been stated. Spotting the ball is extraordinarily inexact. And then when there is a measurement the officials sometimes believe that they are accurate to within an inch or so. Sometimes I’ve seen referees get out pieces of paper to see if the ball has made it to the marker. But how do we know the chains are exactly 10 yards apart? How do we know that all the lines on the field are straight? How do we know which link of the chain the clip is on is an accurate representation of where the markers should be placed? It’s all a series of lies that we all buy into. Oh well, I guess we’ll get by. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [October 31, 2004, 2:54pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/5 "2004-10-31T14:54:25Z")
> [@](#): > > But how do we know the chains are exactly 10 yards apart? Well, … see the story “First and ten, plus 6” here: [http://www.hornetfootball.org/documents/lighter\_side\_news.htm](http://www.hornetfootball.org/documents/lighter_side_news.htm) A high school in Helena, MT had chains that measured 10 yards, 6 inches. They appear to have used them for 3 years before anybody noticed: > [@](#): > > The error wasn’t noticed until the second half of the season-opening high school football game between Helena Capital and Missoula Hellgate last month. Hellgate started a possession on its 20-yardline, and ended up going for it on fourth-and-short. After the play, the nose of the ball was on the 30-yardline, but a measurement with the chains showed Hellgate was still a few inches short of a first down. ---
**Author:** ![racer72](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/racer72/32/3075_2.png) [@racer72](https://boards.straightdope.com/u/racer72)\ **Post date:** [October 31, 2004, 3:29pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/6 "2004-10-31T15:29:04Z")
> [@yabob](#): > > As for keeping them straight, they just eyeball it. A few degrees won’t actually make that much difference - sin(85 degrees) is about .996. The side judge marks the location on the sideline for the chain crew. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [October 31, 2004, 3:37pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/7 "2004-10-31T15:37:21Z")
Which doesn’t help with making sure that they keep the chain straight, as I meant it - parallel to the sides of the field when they stretch it out - I should have worded it better. AFAIK, they just do that by eye, and my point was that being crooked by a few degrees don’t make much difference. ---
**Author:** ![BobT](https://avatars.discourse-cdn.com/v4/letter/b/8e8cbc/32.png) [@BobT](https://boards.straightdope.com/u/BobT)\ **Post date:** [October 31, 2004, 6:23pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/8 "2004-10-31T18:23:08Z")
There have been many other methods of measuring first downs that have been patented and I’ve seen a few in use, but apparently football people like the system they have. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [October 31, 2004, 9:10pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/9 "2004-10-31T21:10:26Z")
> [@BobT](#): > > It’s all a series of lies that we all buy into. Hou about “a series of approximations”? ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [October 31, 2004, 9:22pm UTC](https://boards.straightdope.com/t/american-football-question-measuring-for-a-first-down/272075/10 "2004-10-31T21:22:57Z")
> [@BobT](#): > > It’s all a series of lies that we all buy into. Oh well, I guess we’ll get by. It’s not lies at all. Measuring for a first down doesn’t purport to be an “extremely accurate” technique for determining how far the offensive team has advanced the ball. It purports to be an extremely accurate technique for determining if the offensive team should be awarded a first down, and in this regard its accuracy rate is 100%. What matters about the measurement system is not that it determines with perfect accuracy how far the ball has been advanced - everyone knows that spotting the ball is a sloppy subject - but that it provides a mechanism for getting on with the game in a way that doesn’t result in disputes.