The compass rose is a series of 3 circles surrounded by numbers. The outer circle is to help you find true north, represented by a star or 0. The inner circle points to the magnetic north pole at the time of the chart's printing. You can use a magnetic compass to navigate with the compass rose as a guide. Keep in mind that the magnetic field over the Earth changes over time, so you will need a magnetic compass or an updated map to make use of the compass rose. These buoys mark water channels. The colored circles you see on a chart correspond to buoys you will see floating along the channels as you travel. Travel markers are numbered, making tracking your route easy. Red markers show the right side of a channel, while green markers show the left side. The different colors keep you oriented no matter which way you travel. The anchor is a familiar symbol on charts showing waterways close to land. An anchor means you can let down your boat's anchor safely in that area. Anchoring points may be labeled with numbers or descriptions to describe what kind of boats are allowed to stay there. For example, an anchor point marked "DW" means deep water. Only deepwater vessels will anchor there. A number like 24 stands for 24 hours, so you can only keep your boat in the area for a day at a time. Dangerous obstacles like rocks and shipwrecks are all circled. Some circles are dotted, meaning that the obstacles are submerged. If the lines are solid, the obstacles are at least partially above the water. Many modern charts now mark these spots in purple. Obstacles are generally represented by circles with symbols like asterisks and plus signs. There are many different symbols and they often vary between charts. Some charts use picture symbols, such as a boat to represent a partially-sunken shipwreck. Currents are indicated by arrows with numbers over them. The direction of the arrow tells you which way the current moves. The number lets you know the water speed in knots. Currents and tides change all the time. Take the arrows as a prediction for the way water normally flows. Keep watch as you travel for anything out of the ordinary. Since charts have a limited amount of space, mapmakers have to rely on abbreviations to label markers. Some letters indicate the type of seafloor. Others label landmarks like towers, wharves, and government stations. Some common seafloor abbreviations include S for sand, M for mud, and C for coral. Rky stands for a rocky floor. Tr indicates a nearby tower, while Whf stands for wharf and Bn means beacon. CG may indicate a Coast Guard station on a U.S. map. The full title of the chart is NOS Chart No. 1: Symbols, Abbreviations, and Terms. It isn't actually a sea chart, but it contains a list of all the chart symbols you may encounter. Download it from the NOAA's website or purchase a copy from a commercial chart vendor. The chart covers all U.S. charts. Download a copy at https://nauticalcharts.noaa.gov/publications/us-chart-1.html. Charts made in other countries may have different symbols. Check with your government's maritime office for a reference.
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One-sentence summary -- Use the compass rose to identify the direction you are traveling. Follow red and green buoys for navigational guides. Look for anchors to find anchoring points for boats. Note rocks and other dangers circled on the map. Follow arrows for the speed and direction of currents and tides. Read abbreviations to identify important features in the area. Download a separate chart for a list of less common symbols.

While you may be able to use this article as a guide to help you figure out if you are injured, you still must go to the doctor to get a professional diagnosis. It would be bad to think that you are ok, only to put pressure on your knee and injure it further. Schedule an appointment for as soon as possible after the injury. If you can, you may also go to the hospital to deal with the injury right away. When your ACL gets injured, it is referred to as a sprain rather than a broken bone because it is a ligament (though it can feel as painful as breaking a bone). The term 'sprain' refers to more than just the stretching of the ligament, it is actually the classification the is used to refer to ligament injuries. There are three levels of ACL injury. A grade 1 ACL sprain involves mild injury to the ligament. It has been slightly stretched but not torn. It can still sustain the knee joint and will help the leg remain stable. A grade 2 ACL sprain is when the ligament is stretched beyond its capacity to the point it becomes loose. This is when the technical term "partial tear of the ACL" is used. A grade 3 ACL sprain makes the knee joint unstable and the ligament is completely torn apart. You must have a doctor do this testdo not try it yourself. This is the preferred test for figuring out if you have a partial ACL tear because it can show that you have a partial tear even when the rest of the ligaments and tendons in your knee are uninjured. A doctor will: Have you lie down on a table. Your doctor will first look at your uninjured knee to see how far your shin moves forward when your knee is bent. Your ACL keeps your shin from moving very far forward. Your doctor will then look at your injured knee and see how far your shin moves forward when the knee is bent. If it moves forward further than normal but your doctor can still feel resistance, it means that you have a partial tear. If there is no resistance, your ACL has been fully torn. This test is meant to determine how much pressure can be put on your injured knee before it becomes unstable. Your doctor will move your injured leg a little ways away from your body (this is called hip abduction). She will then: Straighten your leg while simultaneously press inward against the outer part of your knee and twist your leg outward. Doing this will show how well your ACL is functioning because it is a movement that only involves the ACL. Your leg will be slowly bent while continuous pressure is put on it. When your knee is bent at a 20 to 40 angle, your doctor will look at your shin bone. If the bone slides forward a bit it means that your ACL has been partially torn. While the ACL cannot be seen through an x-ray, your doctor can look for other evidence that you ACL has been partially torn. An x-ray of both knees is necessary to detect signs of injury such as fracture, improper alignment of the bony structures, and narrowing of the spaces between joints. All three of these injuries are associated with a partial ACL tear. Unlike an x-ray, an MRI will help your doctor to examine your soft tissue structures in your knee, including your ACL. Your doctor will also look at your meniscus and other knee ligaments to make sure that they are not injured. Your doctor might also request an oblique coronal image if he or she is still not sure about the extent of your injury. This image will give the doctor a better view of your knee in addition to the MRI.
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One-sentence summary --
Go to a doctor if you notice any of the symptoms listed in this article. Be aware that there are three grades of ACL injury. Have a doctor perform the Lachman test. Be prepared for the Pivot Shift test. Have an x-ray taken of your knee. Know that an MRI might need to be done.